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1 | Strengthening teaching and learning of forces in Key Stage 3 science| Notes for participants

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Evaluation: Strengthening teaching and learning of forces in Key Stage 3 science

For completion by teachers

What were the most successful aspects of today’s sessions?

What changes would you suggest if today’s sessions were repeated?

Please grade each session on the basis of how well structured and organised itwas to meet the learning objectives identified.

School ________________________________________________________

Post held ________________________________________________________

Please return this form to your tutor before leaving.

| Strengthening teaching and learning of forces in Key Stage 3 science| Notes for participants


Key Stage 3 National Strategy

Science

SessionGrade: please ring

Comment1 = Very good, 4 = Poor

Pre-unit tasks 1 2 3 4

1 What do pupils know about forces 1 2 3 4and the use of ‘force arrows’?

2 Visualisation of forces and their 1 2 3 4effects

3 What do pupils know about forces 1 2 3 4and motion?

4 Teaching and learning about forces 1 2 3 4and motion

Overall grade for the unit 1 2 3 4



Slide 1.0

Session 1 What do pupils know about forces and the use of ‘force arrows’?

Slide 1.1

Structure of today

Session 1 What do pupils know about forces and the use of ‘force arrows’?

Session 2 Visualisation of forces and their effects

Session 3 What do pupils know about forces and motion?

Session 4 Teaching and learning about forces and motion

Slide 1.2

Objectives for the unit

• To consider how diagnostic questions can be used toidentify what pupils know and identify areas for development

• To identify what pupils have been taught in Key Stages 1and 2

• To explore the use of ‘force arrows’ as a teaching model

• To explore some of the forces that are difficult to visualise

• To identify pupils’ ideas and common misconceptions aboutforces and motion

• To illustrate the use of diagnostic questions in thedevelopment of pupils’ understanding of forces and motion

• To develop a procedure and rules for analysing motion andidentifying the forces acting

• To apply these rules to a range of simple examples of linearmotion

Handout 1.2



Slide 1.3

Objectives for session 1

• To consider how diagnostic questions can be used toidentify what pupils know and identify areas fordevelopment



By the end of this session participants should:

• be familiar with the use of diagnostic questions to identifywhat pupils already know and areas for development;

• recognise that topics taught during Key Stages 1 and 2underpin the key scientific idea of forces at Key Stage 3;

• be more confident with the use of force arrows and theiruse as a teaching model.

Slide 1.4

Diagnostic question sets

• Identifying forces

• The link between force and motion

• Friction

• Gravity and freefall

• Forces in pairs: Newton’s Third Law

Slide 1.5

Task A Reflecting on the questions that youused with your pupils

• What did you find out about– their knowledge and understanding of forces?– the way that they used ‘force arrows’?

• If you managed to use the questions with both Year 6 andYear 7 pupils, how did their responses compare?

• What, if anything, could you do differently in order to get themost out of your use of these questions with another class?

Share your reflections with a neighbour.



Slide 1.6

Pushes and pulls!

Slide 1.7

How teaching at Key Stages 1 and 2 underpins thekey scientific idea of forces at Key Stage 3

4EFriction

2EForces andmovement

3EMagnets

and springs

1EPushes and

pulls

5EEarth, Sunand Moon

6EBalanced andunbalanced

forces

Handout 1.8

Slide 1.9

Forces (contact forces) between objects

• A force exerted on each object lasts for as long as theobjects are in contact.

• Once they are apart, the forces no longer exist and theinteraction has ended.

• The forces (pushes or pulls) arise during the interaction.

• A force cannot be ‘put into’ or ‘stored in’ an object.



Slide 1.10

Task B An example of forces from Key Stage 2

• Draw a diagram of a floating object in a beaker of water.

• Working with a neighbour, share your diagrams giving anyadditional verbal explanation if necessary.

• Explain, in particular, how you used ‘force arrows’ on asheet of paper.

Handout 1.11

Slide 1.12

Why use ‘force arrows’ to represent forces?

• Forces cannot be observed directly.

• ‘Force arrows’ provide:

– a useful way of showing the forces acting on objects in agiven situation;

– an indirect way of identifying when and where a force isacting as well as the direction of the force;

– a way of simplifying/modelling a complex situation so thata prediction can be made about what will happen.

Slide 1.13

Force arrows

An acceptable teaching model

• Forces can be measured using non-standard measures,such as the stretch of a spring or elastic band, or standardmeasures using a forcemeter.

• The length of a ‘force arrow’ can be used to give anindication of the size of the force.

• The direction of a ‘force arrow’ is more important than theprecise point at which it acts.



Slide 1.14

Task C Identifying forces in everyday situations

• In this task, you will see a selection of interactions.

• Each interaction will be shown in 3 ways:

Video clip ➞ animation ➞ diagrammatic representation.

• Identify and label the forces acting on the posters providedusing the arrow-shaped sticky notes.

• After each situation, show your labelled diagram and beprepared to justify the force arrows you have used.

Handout 1.15

Handout 1.17

Slide 1.16

Process of identification of forces

• Identify which forces are acting.

• Identify where the forces are acting.

• Identify the size and direction of the forces.

Slide 1.18






• be familiar with the use of diagnostic questions to identifywhat pupils already know and areas for development;

• recognise that topics taught during Key Stages 1 and 2underpin the key scientific idea of forces at Key Stage 3;

• be more confident with the use of force arrows and theiruse as a teaching model.



Slide 2.0

Session 2 Visualisation of forces and their effects

Slide 2.1

Objective for session 2



• have a greater understanding about forces that are difficultto visualise;

• know some ways to help pupils overcome some of thechallenges experienced when learning about these forces;

• know more about the teaching and learning of specificforces.

Slide 2.2

Forces that are difficult to visualise

Forces that act at a distance, such as:

• gravity;

• magnetism;

• electrostatic forces.

Forces exerted by inanimate objects, such as:

• the reaction of a surface;

• friction.

Robin Millar, University of York, 2002

Handout 2.3

Handout 2.4

Handout 2.5

Handout 2.6



Slide 2.7

A summary of three forces that are difficult tovisualise

Force of gravity:

• the force exerted by the Earth on an object is a typicaleveryday example;

• is really an interaction involving two objects and thereforetwo forces.

Friction:

• is an opposing force to motion, not a resisting force.

Tension:

• a string, holding an object, exerts an upward force equal tothe downward force of gravity on the hanging object.

In all of these cases, we are considering one part of aninteraction which really involves a pair of forces.

Slide 2.8

Task D

Working in a pair explore tension and one other force.

• Tension, and

• Gravity or friction

Report back to the group on how the activity has influencedyour ideas about teaching and learning in this aspect of aforces topic.

Handout 2.9

Handout 2.10

Handout 2.11

Handout 2.12



Slide 2.13

Force from a mattress

• What evidence is there that the mattress is pushing theperson upwards?

Slide 2.14

Force from cushion flooring

• Can you see how the flooring is pushing the personupwards?

• What is different about this example compared to the lastone? Why?

Slide 2.15

Force from hardwood flooring

• Can you see how the flooring is pushing the personupwards?

• Does this mean the floor is no longer pushing the personupwards? Explain your answer.

• What is different about this example compared to the lastone? Why?

Slide 2.16

Task E

Having considered forces that are difficult to visualise, look atthe following diagnostic questions and reflect on theresponses you would expect from the pupils you teach:

• diagnostic questions sets 3 and 4



Slide 2.17

Objective for session 2



• have a greater understanding about forces that are difficultto visualise;

• know some ways to help pupils overcome some of thechallenges experienced when learning about these forces;

• know more about the teaching and learning of specificforces.



Slide 3.0

Session 3 What do pupils know about forces and motion?

Slide 3.1





• be aware of the most common pupil misconceptions andmisunderstandings that teachers are likely to encounterwhen teaching forces at Key Stage 3;

• have identified a number of ways to approach the teachingof forces so that misconceptions and misunderstandingsare revealed and challenged.

Handout 3.2

Slide 3.3

How teaching at Key Stage 2 underpins the keyscientific idea of forces at Key Stage 3

4EFriction

2EForces andmovement

3EMagnets

and springs

1EPushes and

pulls

5EEarth, Sunand Moon

6EBalanced andunbalanced

forces



Slide 3.4

Task F

• Use the forces cards to construct a mind-map of thoseaspects that are taught across Key Stage 3.

• Start by selecting the cards that are most challenging forpupils.

• Leave plenty of space between cards, so that otherstatements and useful information can be added.

• Compare your own mind-map with the version on handout 3.5.

Handout 3.5

Handout 3.6

Handout 3.8

Slide 3.7

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Slide 3.9

Slide 3.10

Slide 3.11a

Task H Diagnostic questions

Individually

Answer the questions from the diagnostic question set,Forces and motion 2: the link between forces and motion.Don’t take too long over each question – your initial ideas arewhat are needed at this stage.

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Slide 3.11b

In pairs or threes

Discuss your answers with a colleague – concentrate on thequestions where your answers are different.

Come to a common view of the correct answer and add anynotes to help you explain your reasoning.

Consider where the question challenges commonmisconceptions and how you would need to seek to addressthese in your teaching.

You are going to present your group’s reasoning behind oneof questions 17–20 to the whole group.

This will include ways in which you might address pupils’misconceptions and misunderstandings.

Slide 3.12





• be aware of the most common pupil misconceptions andmisunderstandings that teachers are likely to encounterwhen teaching forces at Key Stage 3;

• have identified a number of ways to approach the teachingof forces so that misconceptions and misunderstandingsare revealed and challenged.



Slide 4.0

Session 4 Teaching and learning about forces and motion

Slide 4.1




By the end of the session participants should:

• be more confident in applying the procedure and rules tolinear motion in a range of classroom and simple out-of-classroom situations;

• have further developed their understanding of Newton’sFirst Law of Motion.

Slide 4.2

The procedure

• Identify all the forces acting on the object you are interestedin, noting their directions.

• Add the forces acting on the object to find the resultant (ortotal) force acting on it.

Apply the following rules:

• If there is a resultant force acting on an object, this willcause a change in its motion, in the direction of the force.

• If the resultant force acting on an object is zero, its motiondoes not change.

Handout 4.3

Handout 4.4

Handout 3.2



Slide 4.5

Applying the rules

• If an object is moving in a straight line with increasingspeed, there is _________ (no / a resultant) force acting onthe object, in the direction __________( of / opposite to) itsmotion.

• If an object is moving in a straight line and is slowing down,there is __________ force acting on the object, in thedirection ___________ its motion.

• If an object is stationary, the resultant force acting on it is_________.

• If an object is moving at a steady speed in a straight line,the resultant force acting on it is ____________.

Handout 4.6

Slide 4.7

Plenary




By the end of the session participants should:

• be more confident in applying the procedure and rules tolinear motion in a range of classroom and simple out-of-classroom situations;

• have further developed their understanding of Newton’sFirst Law of Motion.

Handout 4.8



Slide 4.9

Objectives for the unit









Objectives for the unit• To consider how diagnostic questions can be used to identify what pupils know

and identify areas for development

• To identify what pupils have been taught in Key Stages 1 and 2



• To identify pupils’ ideas and common misconceptions about forces and motion

• To illustrate the use of diagnostic questions in the development of pupils’understanding of forces and motion

• To develop a procedure and rules for analysing motion and identifying theforces acting

• To apply these rules to a range of simple examples of linear motion



Handout 1.7Handout 1.2



Some key features about forces that pupils need to know in Year 7• An important feature in helping pupils to make progress in their knowledge and

understanding of forces is to build on what they already know from Key Stages1 and 2.

• During Year 7 pupils should apply their knowledge and understanding of forcesin everyday situations.

• The following situations need to be exemplified:

– the identification of the forces acting when an object speeds up, or slowsdown, or changes its direction of movement (generally contact forces);

– the identification of the forces acting when the shape of an object changes(compression forces).

• Frequent application will help pupils develop a precise knowledge andunderstanding that forces always arise from an interaction between twoobjects, and that:

– during this interaction, both objects experience a force – in oppositedirections;

– therefore, forces always arise in pairs – one force on each object involved inthe interaction.



Handout 1.8



Examples of Year 6 pupils’ 1 of 2

work on floating and sinking



Handout 1.11



2 of 2



Handout 1.11



Book lying on table 1 of 13

27 | Strengthening teaching and learning of particles in Key Stage 3 science| Notes for participants





Box sitting on floor 2 of 13






Apple hanging on tree 3 of 13






Ship at sea 4 of 13






Space shuttle launch 5 of 13






Tomatoes on scales 6 of 13




06 5

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Tug-of-war 7 of 13






Dogsled and huskies 8 of 13






Boxer with pummel-ball 9 of 13






Ice hockey game 10 of 13






Astronauts in weightlessness 11 of 13






Ten-pin bowling (1) 12 of 13






Ten-pin bowling (2) 13 of 13






Forces – true or false?Read each statement below and write a T or an F in the second column to indicatewhether you think the statement is true or false.

Statement True or false?

1 The force of gravity is to do with objects falling. Weight is todo with objects feeling heavy.

2 Weight disappears if the air disappears. This is why there isno gravity on the Moon.

3 The weight of an object increases with its height above theground.

4 Weight and mass are the same quantity.

5 Weight increases if the object is compressed and decreasesif the object is spread out.

6 Moving objects try to overcome the force of gravity as theymove upwards and cancel it out at the point where theystop.

7 When a ball is thrown upwards, it stops when the upwardforce on the ball from the hand is equal to the force ofgravity. At this point the force on the ball is zero.

8 The force of gravity acts only while objects are movingdownwards.

9 Heavy objects fall faster than light ones.

10 To push an object along a flat surface, a force equal to theweight of the object must be applied.

11 When an object is pushed on a flat surface for an instant,the force from the hand is cancelled out by friction and thisis why the object stops.

12 Constant motion (i.e. steady speed) requires a force.

Based on questions provided by Bradford College Department of TeacherEducation.






Developing pupils’ visualisation skills in science






Forces that are difficult to visualise 1

Force due to gravity

Gravity is an everyday force experienced by all. Children start to experience andinvestigate the effect of gravity at an early age. At Key Stage 1 and 2 they will haveundertaken activities such as filling plastic containers with feathers and modellingclay. Pupils are asked to predict which container will hit the ground first. The pupilsare then asked to close their eyes and state which container hits the floor first.When completed they cannot distinguish which hits the floor first. They alsoundertake investigations with spinners to distinguish air resistance from gravity, e.g.QCA scheme of work Unit 6E. However, pupils in Years 6 and 7 find the concept ofgravity challenging.

Like all forces, the force of gravity is an interaction involving two objects. It is one ofa pair of forces. The other force is the force exerted by the object on the Earth. Asthe Earth has such a large mass, this force has no detectable effect on themovement of the Earth. The force on the object is better described as ‘the forceexerted by the Earth on the object’ rather than weight or gravity, as this makesclear both what is causing the force and what it is acting upon.

Gravity is a field force similar to magnetic and electrostatic forces. Field forces arenot like contact interactions, where the force only lasts for the short time that theobjects are touching. Field forces act at a distance and continuously (though theymay change in size as the distance between the objects changes).

There are some common misconceptions about this force which need to beaddressed during Year 7. These include:

• the idea that gravity depends on the atmosphere, so there is no gravity, forexample, on the moon;

• the idea that gravity gets stronger as you go further from the Earth (based onthe observation that objects falling from a greater height land with a biggerbang).







Force due to tension

When a rope is pulled, as in a tug-of-war, there is a force due to tension within therope brought about by the two pulling forces. The same happens when a string orsome other material supports an object. However, the forces here act verticallydownwards and upwards. Within the string, where stretching of the fibres occurs,elastic forces act to resist the separation of the particles which make up the fibres.The string exerts an upward force of just the right size to balance the downwardforce of gravity on the object. Because they act in opposite directions to each otherthey balance each other out (which is equivalent to saying that they ‘add to zero’).The force due to tension is equal in size to the weight of the object.

All materials, for example rope or string, have a specific limit related to the forcedue to tension. If the force due to gravity exceeds the limiting value of the force dueto tension for any given material, it will break and any object suspended by thematerial will fall.







Force due to friction

Pupils in Year 7 will be familiar with the force due to friction from Key Stage 2. Theywill have participated in activities, such as using a forcemeter to measure the forceneeded to drag an object across the floor, or dropping objects of different shapesinto a tall cylinder of water.

Pupils will know that friction arises when any two surfaces move over one another.They will also know that air resistance and water resistance can also be thought ofas forces due to friction, caused by the movement of something through the air orwater. However, they will think of friction as ‘resistance to movement’ rather than aforce that acts in the opposite direction to the possible movement of an object.They will have investigated how lubrication affects the movement of one surfaceover another. At Key Stage 3 pupils will explore in more detail the ways in which aforce due to friction can be reduced and situations in which friction is useful.

The type of materials and their texture are important contributory factors, as is thespeed of movement across surfaces. The roughness of the two surfaces will affectthe way that they interact with each other. For example, when sliding a box acrossa floor, the opposing force provided by a smooth floor will be different to that froma carpet. In this situation the force exerted by the carpet on the box will be greaterthan that exerted by the smooth floor.

For a box that is stationary, the horizontal force exerted by the floor on the box (thefriction force) is zero, because there is no sideways force trying to move the box.

For a given box and surface, there will be a maximum limit for the friction force. Ifthe limit of frictional force for the box above is 50N, then any pushing or pullingforce below or at 50 N will not cause the box to move. However, when a pushingor pulling force rises above 50 N the box will move in the direction of this force. Inthe diagram below this can be calculated as follows:

• a pushing force of 60N (to the right) will produce a resultant force (or total force)of 10 N acting on the box (i.e. the sum of 60N to the right and 50N in theopposite direction), and so it will start to move to the right.









Circus of activities for use in Task DActivities related to tension:

1 Suspend a 100g mass on a piece of string, hung froma retort stand. Suspend another 100g mass on aspring, hung from a second retort stand. Whathappens when further masses are added to the stringand the spring? What forces are involved? What willhappen eventually and why?

3 Consider a tug-of-war competition. How might thecompetition be different if: – the rope was made of a very elastic material such as

rubber;– the rope was reinforced with steel cords to increase

its strength;– the rope was made from two sections spliced

together at the midpoint – the first being of veryelastic material and the second reinforced with steelcords?

Activities related to the force of gravity:

1 Describe and explain what would happen if you took afootball on a journey to the Moon, and tried to keepplaying a game of ‘keepy-uppy’* throughout all of thefollowing situations: – on take off from the Earth;– in orbit around the Earth;– landing on the Moon.

*Keepy-uppy is the game where a player tries to keep a footballin the air for as long as possible using their feet, knees, chest orhead to kick or hit it.

3 Fill a tall cylinder with dilute wallpaper paste. Drop inobjects of different shapes (but as far as is possible thesame mass) and observe their motion. The challenge isto produce an explanation of observations made interms of the forces acting.

Activities related to frictional forces:

1 Push and pull a large box (a tea chest or somethingsimilar). Concentrate on ‘feeling’ the forces acting bothbefore the box starts moving and as it is movingsteadily. Provide an explanation for what isexperienced.

3 Show a video clip of an ice hockey game. (Use the onefrom session 1 Task C.) Describe how the motion ofthe puck differs from the motion of the ball in a gameof hockey on grass and explain why.

2 Imagine being responsible for setting up a bungeejump. What forces are involved? How do these forcesinfluence the type of material used for the bungeecord?

2 Drop a coin and a feather down a vertical tube whichcan be (a) evacuated and (b) filled with air. Predict whatwill happen and then explain the observations made.

4 Observe the motion of stomp rockets. Explain whatforces make the rocket move upwards and why iteventually falls to the ground.

4 Examine a bicycle (or skateboard). What features makeuse of forces which help the rider go faster and whichslow the rider down (both usefully and not).

2 The challenge is to get a trolley (or a model car) fromone end of the runway (plank of wood) to the otherwithout touching it. Provide an explanation of what wasdone and why. Amend the challenge so it is to makethe trolley move at constant speed along the runway.What forces are now acting? What would happen if thesurface of the runway was changed? For a particularchange, explain why.



Extended reading stimulus 1 of 3




Extract from Science Web Reader Physics, Nelson Thornes (Publishers)Ltd, 2001.





Handout 2.10

2 of 3






Handout 2.10

3 of 3




Over the top




(Tim Furniss/Genesis Space Photo Library)



Forces that are difficult to 1 of 2

visualise 4

Reaction (of a floor or other surface)

After being taught about a range of forces, including gravity, tension and friction,pupils in Key Stage 3 will begin to understand the reaction (of the floor or othersurface) that exists when objects are placed on a surface, or when a force isapplied to a surface.

A traditional demonstration at Key Stage 3 is to place a textbook on a surface,such as a table, and to then ask pupils to state which forces are acting. Usingelicitation questions, the teacher gets pupils to appreciate that although the Earthexerts a force on the textbook (its weight), pulling it downwards, it does not move.Therefore there must be a force acting upwards. This is called the reaction force.Many pupils, and adults, find it hard to understand that an object placed on a tabledoes not fall due to the force of gravity because the table is pushing upwards withan equal force in the opposite direction.

A good way to allow pupils to experience the force is to provide them with spongesthat they can push and see the force acting back as they remove the depressionforce. Another good way to demonstrate the force is to obtain a ‘cut out’ section ofmattress that a pupil can stand on. If a spring mattress is not available a block ofhigh density foam could be substituted.

The same, or another, pupil can then be asked to stand on a type of cushionflooring. Pupils can then be asked to explain where the force, which is pushing theperson upwards, is coming from.






Finally a pupil can be asked to stand on a hardwood floor whilst others explainwhere the force that is pushing the person upwards is coming from.

Hopefully pupil discussion will lead to the explanation that, although the woodenfloor did not visibly distort under the weight of the person, at a microscopic ormolecular level it did.

There is a limit to the size of the reaction force which the floor can exert on theperson or object placed upon it. Once the weight exceeds the maximum reactionforce that the floor can produce, the floor breaks!

As an additional activity, pupils can be asked to hold a small table and/or laboratorystool up, outstretched in their arms, at 90° to the body. They are then asked todescribe what they are doing to hold the small table and/or laboratory stoolstationary. This provides the opportunity for pupils to experience the ‘upward’ forcerequired to hold the object stationary.






Pupils’ statements about forces

If there is motion there is a force acting

If there is no motion, then there is no force acting

There cannot be a force without motion

When an object is moving, there is a force in the direction of its motion

A moving object stops when its force is used up

A moving object has force within it which keeps it going

Motion is proportional to the force acting

A constant speed results from a constant force

Force is a property of a single object rather than a feature of interaction betweentwo objects

The ‘passive’ partner in an interaction doesn’t exert a force

The ‘push back’ is greater when an object that is pushed doesn’t move than it isif the object does move

An object which is being pushed where there is little friction does not exert any,or much, ‘push back’

The sizes of the forces in a pair depend on the masses of the objects, or theirmotion

Friction only occurs between solids

Friction depends upon movement

Gravity only affects heavy things

It is possible to have weight without gravity

Heavier objects fall faster

Where there is no air there is no gravity

Gravity increases with height above the surface of the earth

Sources: Making sense of secondary science, Driver et al, Routledge 1994 (ISBN 0-415-09765-7) EPSE: Diagnosing pupils’ understanding, University of York Science EducationGroup 2002








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An outline of the ideas about 1 of 2

falling objects developed throughout history Four key figures are important in a potted history of ideas about forces. The part eachone played is outlined below.

The Greek philosopher and scientist Aristotle (~340 B.C.) supported the then popularidea that heavier objects fall faster than light ones, reasoning that this is because‘bodies fall with speed proportional to their weights’. This was, after all, what was, andstill is, commonly observed.

During the 14th Century a group of Parisian philosophers, including Buridan, devised analternative set of explanations for motion which included the idea that force is containedwithin a body. A very common task given to pupils (and adults) requires them to drawthe forces acting on a ball which is thrown vertically upwards then falls to the ground.

Galileo Galilei (1564–1642) was an Italian scientist and a professor at Pisa and Padua.He realised that Aristotle had not considered carefully the effects of air resistance. In




Slide 3.7

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Handout 1.7

one of his many famous ‘thought experiments’ Galileo reasoned that, for objects fallingfreely in a vacuum, there were two rules:

• all falling bodies fall with the same motion; started together they fall together;

• the motion is one with ‘constant acceleration’, that is the body gains speed at asteady rate; it gains the same addition in speed in each successive second.

It is uncertain whether Galileo ever actually performed the famed experiment ofsimultaneously dropping a heavy and a light object from the leaning tower of Pisa. Invarious stories the objects are described as a steel and a wooden ball or two iron ones.It is worth recalling, however, that the experiment was more recently carried out on theMoon where the two objects did, indeed, reach the surface together.

Not long after, the development of air pumps allowed Newton (1642–1727) to actuallycarry out an experiment looking at free fall in a vacuum. He used a guinea (gold coin)and a feather in a long glass tube from which the air had been pumped and showedthat they fell together. It isn’t recorded whether this was done before or after an applefell on his head! (For more of that and other aspects of Newton’s work see, amongstother sources, The Faber Book of Science.) Later, Newton went on to develop hisstatements of the Laws of Motion and of Universal Gravitation.

As an aside, some historians attach significance to the coincidence of the usual datesgiven for Galileo’s death (1642) and Newton’s birth (also 1642). However, Galileo diedon January 8th 1642 whereas Newton was born on January 4th in 1643. The anomalyin the dates is due to the change in the calendars. The Julian calendar places Newton’sbirth on Christmas Day 1642 whilst the Gregorian calendar is used for the date ofGalileo’s death.

The reference to Newton’s use of a vacuum in his experiment provides a reminder thatin so many of the ideas associated with forces we are asking pupils to imagine orvisualise a world where there is no friction, either in the form of air resistance orbetween solid surfaces. Many pupils find this a difficult conceptual leap and teachersneed to pay careful attention to the way they help pupils to develop this different way ofthinking about an imaginary world.

Handout 3.6

Slide 3.10

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Task GA ball is thrown straight up into the air a small distance. After reaching the top of itsflight it falls straight down.

Draw arrows to show any forces acting on the ball as it moves upwards.

Draw arrows to show any forces acting on the ball when it is at the top of its flight.

Draw arrows to show any forces acting on the ball as it is moving downwards.




Path of the ball



Forces and motion

The basic principle

• The motion of an object can be explained by considering the forces acting on it

The procedure, including two important rules:

1 Identify the object whose motion you are interested in.

2 Identify all the forces acting on this object, noting their directions.

3 Add the forces acting on the object to find the resultant force acting on it.

4 Use the following two rules:

• if there is a resultant force acting on an object, this will cause a change in itsmotion, in the direction of the force;

• if the resultant force acting on an object is zero, its motion does not change.

Applying the two rules requires that pupils understand what counts as a ‘change ofmotion’ :

• A change of motion means that the object changes its speed or thedirection in which it is moving

Therefore, an object at rest (stationary) or one that is moving at a constant speed ina straight line is not changing its motion. In these situations, the resultant forceacting on the object is zero. Conversely, an object that is moving in a curved path(e.g. a circle) at a constant speed is experiencing a change in its motion. In thissituation, there is a resultant force acting on the object.

For objects moving in a straight line, the rules lead to the following conclusions.

When there is a resultant force (which is not zero) acting on an object:

• a stationary object will start to move in the direction of the resultant force, andits speed will steadily increase;

• an object moving in the direction of the resultant force will continue moving inthat direction with its speed steadily increasing;

• an object moving in the opposite direction to the resultant force will continuemoving in that direction with its speed steadily decreasing to zero. If theresultant force continues to act, the object will then start moving in the oppositedirection (i.e. in the direction of the resultant force) with its speed steadilyincreasing.

When the resultant force acting on an object is zero:

• if the object is stationary, it will remain stationary;

• if the object is moving, it will continue moving at a steady speed in the samedirection.






Understanding constant speed (uniform motion)Almost all pupils in Key Stage 3 will think that an object moving with steady speedrequires a net force to keep it moving. Their experience, and that of most adults, isof a world where they have come to terms with friction. In order to move somethingthey have to continue to apply a force so that the object moves in the direction ofthe force.

Newton’s First Law of Motion can be described in a number of ways, but generallystates that every object moves in uniform motion, in a straight line, unless actedupon by some external force. Such conditions only exist in the type of ‘perfectworld’ (one without friction) that physicists use to help explain the motion ofobjects. However, in the ‘real world’ frictional forces act on an object, usually withan opposing force to the one that is trying to move the object.

When an object is moving at constant speed the resultant force (or total force) iszero, that is the driving force and opposing forces balance each other out. Astationary object is therefore just a special case of steady motion. In terms ofresultant forces, there is no difference between being at rest, and moving uniformly(at a constant speed in a straight line).

Objects that have been kicked, hit or thrown

A particular situation that pupils find difficult to interpret is the motion of an objectthat has been set in motion and is now slowing down. Examples include a footballthat has been kicked and is rolling along the ground, or a ball that has been thrownvertically upwards. In situations like these, many pupils mark a force in the directionof motion. But this force exists only during the interaction that set the object inmotion. Once it has left the foot or hand of the person who made it move, there isno force in the direction of motion. The resultant force is in the opposite direction,making the object slow down (and eventually stop, and perhaps start moving in theopposite direction).








1 o

f 6

Act

ivit

y 1

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

A p

arac

hutis

t ju

mps

from

a p

lane

. S

he fr

ee fa

lls fo

r a

few

mom

ents

th

en o

pens

her

par

achu

te. S

ome

time

late

r sh

e re

ache

s th

e gr

ound

.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

a ch

ange

in

its

mot

ion,

in t

he d

irect

ion

of t

he fo

rce;

–if

the

resu

ltant

forc

e ac

ting

on a

n ob

ject

is z

ero,

its

mot

ion

does

not

ch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 2

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

You

have

a fl

exib

le t

rack

with

a b

all

bear

ing.

Pla

ce t

he b

all b

earin

g ne

ar

the

top

at o

ne s

ide

of t

he c

urve

an

d pr

edic

t w

here

it w

ill re

ach

on

the

oppo

site

sid

e af

ter

it ha

s be

en

rele

ased

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it a

nd s

ee if

you

wer

e co

rrec

t. C

hang

e th

e sh

ape

of t

he

trac

k an

d tr

y ag

ain.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

ach

ange

in it

s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

nt fo

rce

actin

g on

an

obje

ct is

zer

o, it

s m

otio

n do

es n

otch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Han

do

ut 4

.6





2 o

f 6

Act

ivit

y 3

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

You

have

bee

n gi

ven

an o

ffice

cha

ir w

ith w

heel

s. S

it on

the

cha

ir w

ith

your

feet

aga

inst

a w

all.

Now

pus

h ag

ains

t th

e w

all a

nd e

xper

ienc

e th

ere

sulti

ng m

otio

n.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

a ch

ange

in

its

mot

ion,

in t

he d

irect

ion

of t

he fo

rce;

–if

the

resu

ltant

forc

e ac

ting

on a

n ob

ject

is z

ero,

its

mot

ion

does

not

ch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 4

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

You

have

bee

n gi

ven

a re

ctan

gula

r w

ater

bot

tle a

nd a

tro

ugh

or s

ink

of

wat

er. S

tart

with

the

bot

tle e

mpt

y an

d pl

ace

it on

the

wat

er a

ndob

serv

e w

hat

happ

ens.

The

n ad

d m

arbl

es (o

r sa

nd) a

litt

le a

t a

time

and

put

the

bott

le b

ack

into

the

w

ater

.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

ach

ange

in it

s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

nt fo

rce

actin

g on

an

obje

ct is

zer

o, it

s m

otio

n do

es n

otch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

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doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Han

do

ut 4

.6





3 o

f 6

Act

ivit

y 5

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Firs

t fin

d a

£1 c

oin!

Now

put

it o

n th

e re

ctan

gula

r pi

ece

of c

ard

appr

ox 2

cm x

2cm

, and

bal

ance

th

e co

in a

nd c

ard

on y

our

left

thum

b w

ith t

he c

oin

on t

op.

Pra

ctis

e fli

ckin

g th

e ca

rd a

way

.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

a ch

ange

in

its

mot

ion,

in t

he d

irect

ion

of t

he fo

rce;

–if

the

resu

ltant

forc

e ac

ting

on a

n ob

ject

is z

ero,

its

mot

ion

does

not

ch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

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doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 6

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Imag

ine

you

are

on t

he L

ondo

n E

ye.

Des

crib

e an

d ex

plai

n th

e fo

rces

ac

ting.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

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ject

, th

is w

ill ca

use

ach

ange

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s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

nt fo

rce

actin

g on

an

obje

ct is

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s m

otio

n do

es n

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ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Han

do

ut 4

.6





4 o

f 6

Act

ivit

y 7

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Find

a w

all a

nd le

an o

n it.

Sen

sitiv

e eq

uipm

ent

show

s th

e w

all m

oves

.W

hat

wou

ld h

appe

n if

two

of y

ou

lean

ed o

n it?

Wha

t ab

out

the

who

legr

oup?

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

a ch

ange

in

its

mot

ion,

in t

he d

irect

ion

of t

he fo

rce;

–if

the

resu

ltant

forc

e ac

ting

on a

n ob

ject

is z

ero,

its

mot

ion

does

not

ch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 8

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Ans

wer

thi

s qu

estio

n fro

m K

ey

Sta

ge 3

Sci

ence

tie

r 5–

7, t

est

pape

r 2,

200

3.A

nil s

its o

n a

mat

at

the

top

of a

helte

r-sk

elte

r an

d th

en s

lides

dow

na

chut

e ar

ound

the

out

side

.(a

)N

ame

two

of t

he fo

rces

act

ing

on A

nil a

s he

slid

es fr

om p

oint

A t

o po

int

B.

(b)

As

Ani

l slid

es fr

om p

oint

A t

opo

int

B, t

he fo

rces

act

ing

on

him

are

bal

ance

d. D

escr

ibe

Ani

l’s s

peed

whe

n th

e fo

rces

actin

g on

him

are

bal

ance

d.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

ach

ange

in it

s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

nt fo

rce

actin

g on

an

obje

ct is

zer

o, it

s m

otio

n do

es n

otch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Han

do

ut 4

.6

chut

e mat

A B





5 o

f 6

Act

ivit

y 9

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

a ch

ange

in

its

mot

ion,

in t

he d

irect

ion

of t

he fo

rce;

–if

the

resu

ltant

forc

e ac

ting

on a

n ob

ject

is z

ero,

its

mot

ion

does

not

ch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 10

For

the

activ

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escr

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bel

ow fo

llow

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pro

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re o

utlin

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ure

•Id

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l the

forc

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ctin

g on

the

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ect

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rest

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, no

ting

thei

r di

rect

ions

.•

Add

the

forc

es a

ctin

g on

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obj

ect

to fi

nd t

he r

esul

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(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

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ther

e is

a r

esul

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e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

ach

ange

in it

s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

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rce

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g on

an

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ct is

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o, it

s m

otio

n do

es n

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ange

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es a

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g?2

Wha

t is

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res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

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doe

s th

e m

otio

n of

the

obj

ect

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ge?

4W

hat

are

the

mai

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arni

ng p

oint

s?5

Wha

t ar

e th

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ain

teac

hing

poi

nts?

Han

do

ut 4

.6





6 o

f 6

Act

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y 11

For

the

activ

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escr

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bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

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the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

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pply

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follo

win

g ru

les:

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ther

e is

a r

esul

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ting

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use

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in

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in t

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irect

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of t

he fo

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ltant

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.

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are

the

forc

es a

ctin

g?2

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t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

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doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Act

ivit

y 12

For

the

activ

ity d

escr

ibed

bel

ow fo

llow

the

pro

cedu

re o

utlin

ed.

Pro

ced

ure

•Id

entif

y al

l the

forc

es a

ctin

g on

the

obj

ect

you

are

inte

rest

ed in

, no

ting

thei

r di

rect

ions

.•

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the

forc

es a

ctin

g on

the

obj

ect

to fi

nd t

he r

esul

tant

(or

tota

l) fo

rce

actin

g on

it.

•A

pply

the

follo

win

g ru

les:

–if

ther

e is

a r

esul

tant

forc

e ac

ting

on a

n ob

ject

, th

is w

ill ca

use

ach

ange

in it

s m

otio

n, in

the

dire

ctio

n of

the

forc

e;–

if th

e re

sulta

nt fo

rce

actin

g on

an

obje

ct is

zer

o, it

s m

otio

n do

es n

otch

ange

.

1W

hat

are

the

forc

es a

ctin

g?2

Wha

t is

the

res

ulta

nt fo

rce

and

in w

hat

dire

ctio

n do

es it

act

?3

How

doe

s th

e m

otio

n of

the

obj

ect

chan

ge?

4W

hat

are

the

mai

n le

arni

ng p

oint

s?5

Wha

t ar

e th

e m

ain

teac

hing

poi

nts?

Han

do

ut 4

.6






Follow-up work at school

Name: School:

Actions Year Notes

7 8 9

In m

y o

wn

teac

hing

W

ithi

n th

e d

epar

tmen

t

Give feedback about the course to myhead of department and/or Key Stage3 science coordinator

Report back about the ideas from thiscourse to a department meeting

Help identify other staff who wouldbenefit from attending this training





Handout 1.7

Forces – true or false: 1 of 2

some possible responses

Handout 1.17a


1 The force of gravity is to do withobjects falling. Weight is to do withobjects feeling heavy.

The force of gravity and weight are thesame thing.

2 Weight disappears if the airdisappears. This is why there is nogravity on the Moon.

Weight is independent of whetherthere is air or not.

3 The weight of an object increaseswith its height above the ground.

The weight of an object actuallydecreases with height above theground. This only becomes apparentwhen the distance is large; for smalldistances above the surface of theEarth we assume that the force ofgravity is constant, so our weightremains constant.

4 Weight and mass are the samequantity.

Weight is the force due to gravity andis calculated using Newton’s Law ofGravitation. Weight = mass xgravitational field strength of theplanet. Mass is the amount of matterin an object.

5 Weight increases if the object iscompressed and decreases if theobject is spread out.

Weight does not depend on whetherthe object is compressed or spreadout.

6 Moving objects try to overcome theforce of gravity as they moveupwards and cancel it out at thepoint where they stop.

Moving objects slow down as theymove upwards against the force ofgravity. Objects speed up as they falldown, as they are moving in the samedirection as the force of gravity.Objects cannot cancel out the force ofgravity.





Handout 1.7

9 Heavy objects fall faster than lightones.

They don’t if they are in a vacuum;there they fall at the same rate. Whenair is present, air resistance (friction)slows them down. It isn’t always thelight one that is slowed down the most.It depends on the shape of the object.

10 To push an object along a flatsurface, a force equal to theweight of the object must beapplied.

Incorrect. The force of friction alwaysacts to oppose motion. It slows downall moving objects. The force of gravity(weight) acts vertically downwardswhereas the force of friction acts alongthe surface, in the opposite directionto the movement of the object.

11 When an object is pushed on a flatsurface for an instant, the forcefrom the hand is cancelled out byfriction and this is why the objectstops.

A push from the hand is a contactforce; this stops the instant thecontact stops. The moment the handis removed, the force slowing downthe object is friction.

12 Constant motion (i.e. steadyspeed) requires a constant force.

This is false. The forces on an objectmoving in a straight line at constantspeed are all balanced. There is noresultant force acting on it. If anunbalanced force were acting, theobject would speed up or slow down.

8 The force of gravity acts only whileobjects are moving downwards.

The force of gravity acts on bothupward and downward movingobjects, and on stationary objects.

Forces – true or false?: 2 of 2

answers

Handout 1.17a


Based on questions provided by Bradford College Department of TeacherEducation.

7 When a ball is thrown upwards, itstops when the upward force onthe ball from the hand is equal tothe force of gravity. At this pointthe force on the ball is zero.

Force is not ‘transferred’ from the handto the ball. The instant the ball leavesthe hand the only force on the ball is theforce of gravity. This is the weight of theball. This acts downwards even whenthe ball is moving upwards, so it isslowing the ball down. At some pointthe ball comes to rest momentarily.The force of gravity continues to acton the ball. The ball then begins to fall,speeding up as it does so because ofthe pull of the Earth on the ball.



Documents

Strengthening teaching and learning of forces in Key …wsassets.s3.amazonaws.com/ws/nso/pdf/131d48fb4bc67e5d...using the arrow-shaped sticky notes. • After each situation, show