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Cars. And Forces. Forces Introduction. What do you need in order to balance?. Starter – Say what you know about forces. What is a force? What does it do?. What are forces?. a push. a pull. a turn. You cannot see a force. But you can feel a force and see the effect of the force. - PowerPoint PPT Presentation
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CARSAnd Forces
Forces IntroductionForces Introduction
To be able to:
All Most Some
Describe some of the forces we experience
(Level 4)
Explain that some forces pull and some push
(level 5)
Analyse what forces are acting in different situations
(Level 6)
Starter – Say what you know about forces
What do you need in
order to balance?
What is a force?What is a force?
What does it What does it do?do?
What are forces?What are forces?
What is a force and what does it do?
Identifying Forces - What is a force?Identifying Forces - What is a force?
A force is…
You cannot see a force.
But you can feel a force and see the effect of the force.
Forces make things happen or stop them from happening.Name 5 ways in which you have used a force today.
Label each of these as a Label each of these as a pushpush or a or a pullpull or or bothboth..
Tug- of- war
Answering a phone
Picking flowers
Using a pogo stick
Using a yoyo
Mum starting kids on a slide
PUSH PUSH & PULL
PULL
PULL
PULL
PUSH & PULL
Review
Forces IntroductionForces Introduction
To be able to:
All Most Some
Describe some of the forces we experience
(Level 4)
Explain that some forces pull and some push
(level 5)
Analyse what forces are acting in different situations
(Level 6)
Starter – Say what you know about forces
What do you need in
order to balance?
In each picture, identify the main force and In each picture, identify the main force and describe its effect.describe its effect.
Click on the picture to find the force
Reminder: Link the Labels and the Reminder: Link the Labels and the DiagramsDiagrams
Push Pull Twist
A. B. C.
Practical Practical ActivityActivity
Safety!
Springs?
Observing forces in Action Investigations For each activity, fill in the spaces and draw arrows on the diagram to show the forces. Say if it is a pull or a push. The first diagram is done for you as an example.
A
Weight of item 1 = ……………N Weight of item 2 = ……………N Weight of item 3 = ……………N
Pull
B
Try putting the magnets together in two different ways. What happens as you move the magnets apart? Complete this “It is hard to pull the two magnets apart because the north pole of one magnet attracts the. ……. ……… of the other magnet.”
Try: Then try
C
Hook two Newton meters together with string. Hold each one and pull gently Take at least 3 sets of readings when the meters are steady …….… N ……….N …….… N ……….N …….… N ……….N What happens if forces are not balanced
D
Drop the 2 pieces of paper – see what happens The crumpled paper hits the ground ……………….. than the flat paper. Why?
E
Weight the item in the air and in the water Weight of item in air = …………….. N Weight of item in water = ………… N Why is there a difference?
F
Take the lids of the jars and put them back. Do you use force for this? What sort of force?
weight
Force by Newton meter
N S N S
N S S N
Investigation: Investigation: Observing Forces in Observing Forces in
ActionAction
Types of forcesTypes of forcesThere are many different types of forces.
Some act by contact and are called
‘‘contact forces’.contact forces’.
e.g. hit a ballwind blowing
ocean waves crashing on rocks
Types of forcesTypes of forcesContact forces include:
Applied the force applied to an object by a person or another
object.
Frictional the force exerted by a surface as an object moves across it.
Tension
the force which is transmitted through a string, rope, cable or wire when it is pulled at both ends.
Types of forcesTypes of forces Normal
the support force on an object which is in contact with another stable object.
Spring the force exerted by a stretched spring on
any object attachElastic
Make objects change shapee.g. spring, rubber
ed to it.
Types of forcesTypes of forces
ElasticMake objects change shape
e.g. spring, rubber
Some forces do not need contact to occur, and can act at a distance.
These are called
‘non-contact forces’.
e.g. gravity.
Types of forcesTypes of forces
Types of forcesTypes of forcesThere are 4 non-contact forces:
GravitationalCaused by Earth pulling objects down
Electrical
Due to charged objects
Types of forcesTypes of forces
MagneticDue to magnets
e.g. magnets on fridge, cupboards
Types of Types of ForcesForces
FrictionFriction
BuoyancyBuoyancy
MagnetismMagnetism
ElectrostaticsElectrostatics
ElasticElastic
GravityGravity
• CONTACTCONTACT• CONTACTCONTACT• NON NON
CONTACTCONTACT• NON NON
CONTACTCONTACT• CONTACTCONTACT• NON NON
CONTACTCONTACT
Which of the following are contact/non-contact forces?
What forces are What forces are happening?happening?
Look at the following image
•What examples of forces can you see?•What are the pushing and pulling forces?
•What are the forces being caused by gravity?
• What are the lifting forces?•What are the muscular and electrical
forces?
Forces can affect things in 3 ways. Forces can affect things in 3 ways. Can you name them?Can you name them?
Effect 3. A force can change the direction of an object.
Effect 2. A force can change the speed of an object, making it faster or slower. It can keep it going at the same speed
Effect 1. A force can change the shape of an object.
20 seconds
think time
Be ready to
share!
2 minutes to
share with
your group
What do forces What do forces do?do?
In your groups of 4 think of 4 statements that can describe what
forces can do to this car!!
Hands up!!!
What Forces are acting What Forces are acting upon this car?upon this car?
Gravity/weight
Thrust Air resistance
Friction
Normal
GravityGravityThe force of GRAVITY is
what keeps us on the SURFACE of the
EARTH.
You do not have to be TOUCHING the Earth
to feel the force of gravity.
GRAVITY ON EARTH PULLS YOU DOWN.
GRAVITY ALWAYS PULLS; IT NEVER
PUSHES.
We can draw an arrow on the shark and car to show the direction
of gravity:
Upwards Forces IUpwards Forces IIf there is a downwards force of gravity pulling
on a car then why does it not get pulled into
the ground?
There must be a force PUSHING UP on the car
that stops it getting pulled into the ground.
Gravity
Do you know what we call this force?
The REACTION FORCE.
Reaction
Upwards Forces IIUpwards Forces IIIf there is the downwards
force of gravity pulling down on a floating shark then why does it not sink
deeper into water?
There must be a force PUSHING UP on the
shark that stops it getting pulled further down. Gravity
Do you know what we call this force?
The UPTHRUST.
Upthrust
Force Diagrams exerciseForce Diagrams exerciseLabel the forces acting on a rocket moving through the Earth’s atmosphere.
Thrust
Air resistance
Gravity
Upthrust
Force Diagrams ExerciseForce Diagrams ExerciseLabel the forces acting on the shark.
ThrustFriction
Gravity
Upthrust
WHAT CAUSES THESE CHANGES????
change shape
change direction
Forces Can……Forces Can……
change speed
Direction and Strength of Direction and Strength of ForcesForces
Forces can act upwards, downwards, sideways, or any direction at all.
To show the direction of a force you can use an arrow. You can then
show the strength of the force by the length of the arrow.
A large arrow means a strong force, and a small arrow means a weak
force
32
Force DiagramsForce DiagramsWe use arrows to show
(a)The direction
(b) The size
of forces
The bigger the arrow,
the bigger the force.
Which arrow(s) could show Ellie hitting a nail?
Which could show John lifting a 100N weight –
and which a 200N weight?
A B C D
Balanced and Balanced and Unbalanced ForcesUnbalanced Forces
To be able to:
All Most Some
Say what is meant by gravity(Level 4)
Give examples of forces that don’t need objects to touch(level 5)
Explain why objects speed up, slow down or remain at the same speed(Level 6)
Starter – Why is a motorbike faster than a bicycle?
If forces balance, do
they cancel each other out?
Two equal forces of the same magnitude acting in opposite directions.
i.e there will be no motion until one force is greater than the other
Balanced ForcesBalanced Forces
Unbalanced ForcesUnbalanced Forcescause acceleration because there is an
individual force which is not being balanced by a force of equal magnitude and in the
opposite direction.
i.e when one force is greater than another therefore there will be motion.
Balanced and Unbalanced Balanced and Unbalanced ForcesForces
Consider a car standing on a road. What forces are acting
on it?
Gravity/Weight
Reaction
These two forces would be equal – we say that they are
BALANCED. The car doesn’t move anywhere.
Balanced and Unbalanced Balanced and Unbalanced ForcesForces
Gravity/Weight
Reaction
What would happen if we took the road away?
Balanced and Unbalanced Balanced and Unbalanced ForcesForces
What would happen if we took the road away?
The car’s weight is no longer balanced by
anything, so the car falls downwards…
Gravity/Weight
500 N 500 N
Imagine a car travelling at a constant speed of 50 km/h.
Balanced and Balanced and Unbalanced Forces Unbalanced Forces
The engine provides sufficient force to just overcome all the frictional forces that are
acting to decrease the speed.
The air resistance will decreases because the car has a “tail wind” (it is being blown from behind). This means the forces acting on the car are no longer
balanced.
Balanced and Unbalanced Balanced and Unbalanced ForcesForces
The car will increase in speed (accelerate) until the forces are balanced again.
>50 km/h
500 N 400 N
60 km/h
500 N 500 N
Balanced and Unbalanced Balanced and Unbalanced Forces –summaryForces –summary
If the forces on an object are balanced:
and the object is stationary, it will remain stationary
and the object is moving, it will continue to move at the same speed and in a straight line.
In other words, the object will continue to do what it is already doing without any change.
If the forces are unbalanced, two things can happen:
The speed can change. This is called acceleration.
The direction of motion can change.
What happens to the speed of the car when the thrust and drag forces are unbalanced?
When the thrust and drag forces are balanced, the car travels at a constant speed.
drag thrust
The friction of the tyres on the road
opposes movement of the car.
The friction of air against the body of the car also opposes the car’s
movement.This type of friction is called
air resistance.
What forces are acting on a racing car travelling at a constant speed?
Drag forces oppose the thrust force and slows the car.
Where are these frictional forces?
drag
A thrust force makes the car move forward.
Where does this force come from?
thrust
Forces Forces QuestionsQuestions
Year 7 – Forces Worksheet 7f.2 © ZigZag Education 2006
Balanced and Unbalanced forces
Balanced forces Unbalanced forces Object is stationary The object will stay still. The object will start to move.
Object is already moving The object will continue moving at the same speed.
The object will either speed up or slow down or change direction.
1. The diagram shows 4 people pulling on 4 ropes tied together. If the ropes are not moving, what must the forces be exerted by
a. Mrs South? b. Miss West?
2. The diagram shows a firework rocket. As it flies through the air, there are 3 forces on it.
a. Label the 3 arrows to show the 3 forces b. Label the arrows using these words: weight,
thrust, air resistance. c. What can you say about the forces when the
rocket is just taking off? d. Why does the rocket come back to earth?
3. The diagram shows a submarine. It has 4 forces on it. The names of the four forces are:
i. upthrust from the water ii. the weight of the submarine iii. the drag of friction form the water] iv. the thrust of he engine
a) Put the correct level against each force.
b) If the upthrust happens to be greater than the weight, what happens to the submarine?
c) If the thrust is greater than the drag what happens?
4. The diagram shows a parachutist. a. Label the forces using the correct words. b. If she is falling at a steady speed, what can you
say about the 2 forces? a. If she is accelerating downwards, what can you
say about the two forces?
Mr North 80N
Miss West Ms. East
100N
Mrs South
B C
D
E F
A
• Use the worksheet• Work through the questions by yourself
• Then share your answers with someone else
Measuring ForcesMeasuring ForcesThe unit used to measure force is the Newton (N),
named after Sir Isaac Newton.
The table below gives you some idea of the approximate sizes of some forces.
46
That’s right, I have my
own measuremen
t
Measuring ForcesMeasuring ForcesBeing able to read numbers from scales on measuring instruments is very important.
How much force are these force metres measuring?
(they are also called Newton metres)
0 ______
5 ______
10 __
0 ______
10 ______
20 __
0 ______
25 ______
50 __
1N12N
46N
What force is acting on each Newton Meter?
Reading Newton MetersReading Newton Meters
Click here for answer Click here
for answerClick here for answer
Next to your Next to your Must & shouldMust & should objectives objectives draw either….draw either….
A smiley face if you
understand it
A straight face if you partly
understand it
A sad face if you don’t
understand it
Objectives
Must: Know examples of forces acting upon cars
Should: Know unbalanced forces cause changes in speed and direction
Cars and ForcesCars and ForcesTo be able to:
All Most Some
Students should know examples of forces acting upon objects
MYP (1/2)
Understand that unbalanced forces causes changes in speed and direction
MYP (3/4)
Explain how different forces can affect the motion, speed and direction of a car
MYP (5/6)
Review!
So What Have We Learned So What Have We Learned Today?Today?
In your lab teams:
1) Using the equipment (1 car, 1 piece of sand paper, 1 piece of card).
2) Illustrate what you have learnt about how different forces can affect cars (think about balanced and unbalanced forces).
3) You have 5 minutes to discuss and prepare in your groups.
4) I will randomly choose a group or 2 to feedback to the class.
Team Stand-N Share
Cars and ForcesCars and ForcesTo be able to:
All Most Some
Students should know examples of forces acting upon objects
MYP (1/2)
Understand that unbalanced forces causes changes in speed and direction
MYP (3/4)
Explain how different forces can affect the motion, speed and direction of a car
MYP (5/6)
Review!
Next to your Next to your CouldCould objectives objectives draw either….draw either….
A smiley face if you
understand it
A straight face if you partly
understand it
A sad face if you don’t
understand it
Objectives
Could: Explain how different forces can affect the motion, speed and direction of a car
Why are certain materials used when
building a car?
How are cars designed to limit to make the best use of forces?
Extension WorkExtension Work
What else did you What else did you find out?find out?
weight
Force by Newton meter
N S N S
Record your findings on a concept map
Improve your Concept MapImprove your Concept MapMake sure these words are on
• Friction• Contact• Magnetism• Gravity• Thrust• Upthrust• Mass• Weight• Balanced• Unbalanced• Speed up• Slow down
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HomeworkHomework•Describe at least 10 forces that you
have seen.
•Find a mixture of push, pull and twist.
•Write down the effect each force has.
Your TurnYour Turn
1-9
If you finish, do;
1-4
60
Cars and Forces
To be able to:
All Most Some
Should know examples of forces acting upon objects
MYP (1/2)
Understand that unbalanced forces causes changes in speed and direction MYP (3/4)
Explain how different forces can affect the motion, speed and direction of a carMYP (5/6)
In the circle next to your In the circle next to your objectives draw either…objectives draw either…
Objectives Must: Know examples of forces acting upon cars
` Should: Know unbalanced forces cause changes in speed and direction
Could: Explain how different forces can affect the motion, speed and direction of a car
A smiley face if you feel you know it
A straight face if you feel you partly know it
A sad face if you feel you don’t know it
Homework
Get another picture of your car…Draw accurate force diagrams on it…
Now research how your car is designed to use or overcome the forces acting upon it!