Science on Vacation!

3rd/6th Grade

Greenbriar West Elementary

By Darren McKnight

Fall 2004

Topics• Flying to Colorado

• Driving to Colorado Springs

• Going to the Top of Pikes Peak

• Going to the Pool

Teaching Strategy• Lecture

– Reinforce terms from handout provided by GBW– Interactive – use handout as framework, not many answers

on the sheets– marks the sheets the students will get

• Lab– Provide handout for lab groups to use– Draw the “approved solution” on the board after the lab

• Test/Quiz– Review concepts from lecture and observations from the lab

What is Science?• Science is the methods by which people try to explain

what happens around them– Why does an apple fall down rather than up?– Why do winds blow?– Why doesn’t a swing swing forever?

• Follows the “scientific process”– Observations: note physical activity– Hypothesize: propose an “if-then” explanation– Experiment: organized way to prove or disprove hypothesis by

taking data– Conclusions: make summary statement or equation to represent

how nature behaves

Flying to Colorado

Greenbriar West ElementaryBy Darren McKnight

Fall 2004

Mass – Key Points

• What is mass?

• Does a party balloon have more mass than a candy bar?

• How do you figure out an object’s mass?

Mass – Key Points Answers

• What is mass?– Matter or stuff

• Does a party balloon have more mass than a candy bar?– Bring in one of each; contrast size vs mass – it

depends but probably not

• How do you figure out an object’s mass?– Weigh it; but is mass the same thing as weight? No,

will talk about this in a moment; mass of something is the same no matter what but its weight varies…

Mass and Inertia

• “Inertia is the measure of resistance to change in motion…”– What makes something hard to move? _________

• “Unless acted upon by an outside force, an object remains at rest or an object in motion stays in motion.”– What is an “outside force” that often causes

moving objects to slow down? ______________

Mass and Inertia

• “Inertia is the measure of resistance to change in motion…”– What makes something hard to move?

• If it is heavier – has more mass

• “Unless acted upon by an outside force, an object remains at rest or an object in motion stays in motion.”– What is an “outside force” that often causes moving objects

to slow down?• Friction

Force – Key Points

• What is a force?

• Why does gravity exert a force on you?

• If an object is not moving does that mean that there are no forces on it?

Force – Key Points Answers

• What is a force?– Something that pushes or pulls you

• Why does gravity exert a force on you?– Two objects with mass attract each other, so the Earth

pulls the objects towards it

• If an object is not moving does that mean that there are no forces on it?– It may but it probably means that the forces acting on

an object cancel out

ForcesThe man is standing still.Are there any forceson the man?

If so, draw them.

floor

ForcesThe force due to gravityis the same in size,but opposite indirection, to the forceby the floor!!!!

Floor

Gravity

Gravitational Force - Questions

• So what causes a gravitational force?

Gravitational Force - Answer• So what causes a gravitational force?

– Two objects are attracted to each other

Object 2 (has mass)

Object 1 (has mass)

F1

F2 F1 = F2

Earth

PersonF

F

Fperson = Fearth

•Gravitational force keeps us “stuck” to the Earth!!!

•We actually pull on the Earth but the Earth is too big to move!!!

Universal Law of Gravitation

• F = m (GMe/Re2) = mg

– Where• F = force on an object with mass, m

• G = gravitational constant = 6.7 x 10-11 m3/kg*s2

• Me = mass of the Earth = 5.94 x 1024 kg

• Re = radius of Earth = 6.38 x 106 m

• g = acceleration due to gravity = 9.81 m/s2

• Circle the terms above that are constants

Universal Law of Gravitation

• F = m (GMe/Re2) = mg

– Where• F = force on an object with mass, m

• G = gravitational constant = 6.7 x 10-11 m3/kg*s2

• Me = mass of the Earth = 5.94 x 1024 kg

• Re = radius of Earth = 6.38 x 106 m

• g = acceleration due to gravity = 9.81 m/s2

• Circle the terms above that are constants– But note that G is the only true constant because if

you go to another planet the other terms will vary…

Gravitational Force - Questions

• Is there a gravitational force on a person standing on the moon?– Is it larger or smaller than the gravitational

force on the Earth?

– Why?

Gravitational Force -Answers

• Is there a gravitational force on the moon?– Is it larger or smaller than the gravitational

force on the Earth?• The gravitational force is smaller on the moon.

– Why?• The moon is smaller (less massive) than the Earth.

• It is actually 1/6 the mass so someone’s weight on the Moon would be 1/6 of what it would be on Earth

– A 90 lb student would weigh only 15 lbs!!!!!!

Acceleration Due to Gravity

• Due to the force exerted as a result of the mass of the Earth an object is accelerated (I.e. the speed increases) when released

At time = 0 seconds, an object is released with no velocity

One second later, it is going 9.81 m/s

Therefore, the acceleration due to gravity is 9.81 m/s per secondwhich is the same as 9.81 m/s2

Science Terms• Constant – item that does not change

• Variables – things in an experiment that change

• Independent Variable – variable that is changed

• Dependent Variable – variable that is measured (it “depends” on the other settings)

Weight vs Mass• Weight is a force: W = m g

– m = mass and – g = acceleration due to gravity = 9.81 m/s2

m (kg) W (N)

10 98

5 49

12 118

5 52

18 177

5 47

8 78

Mass, kg

Wei

ght,

N

0 2 4 6 8 10 12 14 16 18 20

40

020

6080

100120140160180

PLOT THE DATA!!

Weight vs Mass

m (kg) W (N)

10 98

5 49

12 118

5 52

18 177

5 47

8 78

Mass, kg

Wei

ght,

N

0 2 4 6 8 10 12 14 16 18 20

40

020

6080

100120140160180

X

X

X

X

X

X

X

Weight vs Mass Experiment

• What observations can you make?

• What is the constant?

• What is the independent variable?

• What is the dependent variable?

Weight vs Mass Experiment

• What observations can you make?– If the mass goes up then weight goes up, plot is a line

(I.e. linear relationship)– Highlight that this is a hypothesis!!!!!

• What is the constant?– Acceleration due to gravity

• What is the independent variable?– Mass in kilograms

• What is the dependent variable?– Weight in newtons

Why does an airplane fly?

• This is a review of force concepts

What are the four forces on an aircraft and wheredo they come from?

Why does an airplane fly?

• This is a review of force concepts

Thrust – created by engines

Lift – caused by flow over wings

This is the interesting one!!!!

Weight – caused by massof the aircraft

Drag – caused by aircraftsurfaces rubbing against air

Force Interactions

• To move forward what must be true?

• To lift off of the ground what must be true?

• How is lift created?

Force Interactions• To move forward what must be true?

– Thrust must be greater than drag

• To lift off of the ground what must be true?– Lift must be greater than weight

• How is lift created?– Due to the curvature of the aircraft wing the air flows over

the top of the wing faster than the bottom of the wing. Air flowing faster creates a lower pressure so the wing is pushed up by the higher pressure on the underside of the wing

Lift from a Wing

AircraftMotion

wing

Air is accelerating around top of wing – drops pressure

PressureFrom air

PressureFrom air

Since pressure islower on top thanon the bottom of the wing, the wingis pushed up!!!

Quiz

Quiz Name______________• What is a force?

__________________• What are two examples of a

force?____________________________________

• What is energy?__________________

• What are two types of energy?____________________________________

• What is the sum of potential and kinetic energy?__________________

• What type of energy is stored when a spring is compressed?____________________

• What is a constant in the spring experiment?______________________

• When the spring is released what type of energy is created?____________________

• Extra Credit: What is another way to store energy in a spring other then compressing it?____________________

Quiz Name______________• What is a force?

Action that causes something to speed up or slow down, like a push or pull

• What are two examples of a force?Gravity, spring, and friction

• What is energy?Ability to do work

• What are two types of energy?Potential, kinetic, mechanical, chemical, and electrical

• What is the sum of potential and kinetic energy?Mechanical energy

• What type of energy is stored when a spring is compressed?Potential energy

• What is a constant in the spring experiment?The stiffness of the spring

• When the spring is released what type of energy is created?Kinetic energy

• Extra Credit: What is another way to store energy in a spring other then compressing it?Lift it up – stores potential energy as it is moved against the force of gravity

KEY

Driving to Colorado Springs

Greenbriar West ElementaryBy Darren McKnight

Fall 2004

Friction – Key Points

• What is friction?

• What makes friction greater?

• What makes friction less?

• What are examples of friction?

Friction• Friction is rubbing – force between two surfaces that

goes against motion of object– create heat or – slow down motion or – Both

• Rough surfaces makes friction greater while smooth surfaces make friction less

• What are examples of friction?• Rubbing hands together to get warm• Putting sand on the road to prevent cars from sliding• Newspaper sliding across the driveway• Any more?

Friction• Three items determine the friction force

– YES, FRICTION CREATES A FORCE!!!• 1. Goes against the motion • 2. Greater if surfaces are rough ; less is surfaces are smooth• 3. Friction increases as mass of object increases

• If we slid a book across the two surfaces below, on which one would the book go farther?

• Draw the forces on the book (pick one).

A B

Friction• If we slid a book across the two surfaces

below, on which one would the book go farther? A

ATable

Book (gravity)

Friction

Force Due to Friction

• Force due to friction, Ff

– Ff = * N• Where = coefficient of friction (constant)

• Where N = mg (weight of the puck acting in opposite direction)

• If the surface is smoother is the coefficient of friction larger or smaller?________

Friction Quiz

• Is friction a force? (Circle one) Yes No• Does friction make an object move faster or does it

oppose motion (I.e slow it down) ? ______________• What is the result of friction on spacecraft when they

come back through the atmosphere? ________________________________________

• If an object has a low coefficient of friction is it smooth or rough? _______________________

Friction Quiz

• Is friction a force? (Circle one) Yes No• Does friction make an object move faster or does it

oppose motion (I.e slow it down) ? _opposes motion_• What is the result of friction on spacecraft when they

come back through the atmosphere? ____it heats up the surface to very high temperatures______

• If an object has a low coefficient of friction is it smooth or rough? ____smooth________________

Going to the Top of Pikes Peak

Greenbriar West ElementaryBy Darren McKnight

Fall 2004

Potential and Kinetic Energy – Key Facts

• What is energy?

• What is potential energy?

• What is kinetic energy?

Potential and Kinetic Energy – Key Facts

• What is energy?– Ability to do work

• Potential energy – “stored” energy– How can we “store” energy?

• Kinetic energy – energy of movement– Ask - How is potential energy converted into kinetic

energy?

Potential Energy

Does the ballhave any storedenergy here?

Does the ballhave any storedenergy here?

Potential Energy

Does the ballhave any storedenergy here?

Does the ballhave any storedenergy here?

NOYES, we moved the ballagainst gravity (did work)

Force Review

What forces are acting on the ball while wehold it still above the floor?

Draw and label them.

Force Review

Which force is greater?They are the same, that is whythe ball is not moving!!!

Force of the hand

Force due to gravity

Potential Energy

What happens when we let goof the ball?

If the ball is to move show the direction of the ball.

Label the forces on the ball!!!!

Potential/Kinetic EnergyWhat happens when we let goof the ball?

It starts to fall – has kinetic energyIf the ball is to move show the direction of the ball.

Label the forces on the ball!!!!Gravity is larger force than air resistance

velocity

Gravity

Air resistance

Energy Summary

• What is the sum of potential and kinetic energy?

• What are two other types of energy?– –

Energy Summary

• What is the sum of potential and kinetic energy?– Mechanical energy

• What are two other types of energy?– Electrical energy: uses negative charge (e.g.

toaster)– Chemical energy: uses chemical reactions

(e.g. battery)

Energy – Key Facts• What is energy?

• What is potential energy?

• What is kinetic energy?

• What is the sum of potential and kinetic energy?

• What are two other types of energy?– –

Energy – Key Facts

• What is energy?– Ability to do work

• Potential energy – “stored” energy– How can we “store” energy?

• Kinetic energy – energy of movement– Ask - How is potential energy converted into kinetic energy?

• What is the sum of potential and kinetic energy?– Mechanical energy

• What are two other types of energy?– Electrical energy: uses negative charge (e.g. toaster)– Chemical energy: uses chemical reactions (e.g. battery)

Going to the Pool

Greenbriar West ElementaryBy Darren McKnight

Fall 2004

Let’s Go Play!

• Liquid, gas, and solid

• Floating

• Swim races across the pool – 25m vs 10m

Last Night in the Hotel

Greenbriar West ElementaryBy Darren McKnight

Fall 2004

Dad Wants a Cup of Coffee

Electricity Basics - Charge

• Atoms are made of neutrons, protons, and electrons– Electrons have negative charge

• Electrons are on the outside of the atom and are easily knocked off

• When electrons are knocked off then an object gets “charged”– Positive if the electrons are knocked off– Negative if the electrons that are knocked off cling to

the object

Materials Related to Charge

• Some materials hold their electrons very tightly– Electrons do not move through them very well.

– These things are called insulators. • Plastic, cloth, glass and dry air are good insulators.

• Other materials have some loosely held electrons, which move through them very easily. – These are called conductors.

• Most metals are good conductors.

Static Electricity

• How can we move electrons from one place to another? _____________

• As electrons move from one atom to another…– Some atoms get extra electrons - net negative charge. – Other atoms lose electrons – net positive charge. – When there is an imbalance of positive and negative

charges like this, it is called static electricity.

Static Electricity• How can we move electrons from one place to another?

– Rub two objects together. If they are made of different materials, and are both insulators, electrons may be transferred (or moved) from one to the other.

– The more rubbing, the more electrons move, and the larger the charges built up.

• Scientists believe that it is not the rubbing or friction that causes electrons to move. It is simply the contact between two different materials. Rubbing just increases the contact area between them.

• As electrons move from one atom to another…– Some atoms get extra electrons - net negative charge. – Other atoms lose electrons – net positive charge. – When there is an imbalance of positive and negative charges like

this, it is called static electricity.

Charged Particle Behavior• If two things have different charges, they attract, or pull

towards each other. If two things have the same charge, they repel, or push away from each other.– If they push each other what must there be? ________________

– What is the size of this “push” dependent on? ___________

Charged Particle Behavior• If two things have different charges, they attract, or pull

towards each other. If two things have the same charge, they repel, or push away from each other.– If they push each other what must there be? force

– What is the size of this “push” dependent on? Charge and distance between the charges

• FORCE – Coulomb’s Law F = k (Q1 Q2)/d2

Real Life Observations

• So, why does your hair stand up after you take your hat off?

Real Life Observations

• So, why does your hair stand up after you take your hat off? – When you pull your hat off, it rubs against your hair.

Electrons move from your hair to the hat. – Now each of the hairs has a positive charge. Things

with the same charge repel each other. – So the hairs try to move away from each other. – The farthest the hairs can get is to stand up and move

away from each other.

Electricity – Use Physics for Good

• “Static” electricity is about charges that just hang around (I.e. static)

• Electricity, as we know it, takes advantage of moving charges to do work– What do we call moving charges? __________– What causes these charges to move?

______________________________________

Electricity – Use Physics for Good

• “Static” electricity is about charges that just hang around (I.e. static)

• Electricity, as we know it, takes advantage of moving charges to do work– What do we call moving charges? CURRENT– What causes these charges to move?

ELECTROMOTIVE FORCE OR VOLTAGE

Electricity Basics – V, i, R

• Voltage is the amount of electrical force measured in volts– Much like potential energy

– A charged particle will accelerate across a voltage difference like a ball being released that is then acted upon by gravity

V1

V0

- Voltage difference created by the two posts of a battery thus causing charges to flow (I.e. CURRENT)

Electricity Basics – V, i, R• If you want charge to flow in a wire (I.e. electricity)

then the flow of charges is called current– Current = i, measured in amperes (or just amps)

• A wire will not let charges flow without some resistance to their flow, this resistance is called resistance!!!– Resistance = R, measured in ohms

– Resistance is like “microscopic” friction

V = i R Ohm’s Law

Effects of Current• There are two effects of current

– Heating effect• “Microscopic friction” creates heat

– Dissipates power (I.e. consumes energy over time): toaster

– Magnetic effect• Moving charges create a magnetic field

– Used in motors and transformers– Makes electricity generation possible

(which is the production of current)– Spinning turbine (powered by steam, wind, water

or many other ways) turns electromagnetsthat are surrounded by heavy coils of copperwire inside generators that create magneticfield that causes electrons to flow – CURRENT!

Types of Current• Direct Current (DC)

– Current flows in the same direction all of the time• Batteries create DC, usually lower voltages

• Alternating Current (AC)– Current direction is reversed in direction at regular

intervals (e.g. 60 Hz – changes direction 60 times a second - in your house)

• Electricity used in your home from outlets, higher voltages (120V)

• Which is better?– DC is more efficient so why do we all have AC in our

houses?_______________________________

Types of Current• Direct Current (DC)

– Current flows in the same direction all of the time• Batteries create DC, usually lower voltages

• Alternating Current (AC)– Current direction is reversed in direction at regular intervals (e.g. 60 Hz

– changes direction 60 times a second - in your house)• Electricity used in your home from outlets, higher voltages (120V)

• Which is better?– DC is more efficient so why do we all have AC in our houses? For

safety reasons, if you grab a high voltage DC line the body will clamp up and not let go, many more electrocutions – all devices driven to AC after original poor safety and human response to DC

Power• Power is measured in Watts

– 1500 Watt blow dryer, for example

• P = i V = current x voltage = V2 / R• We have a 40W light bulb in your

house…– How much current is flowing

through the light bulb?________

– What is the resistance in the lightbulb? ____________

Power• Power is measured in Watts

– 1500 Watt blow dryer, for example

• P = i V = current x voltage = V2 / R• We have a 40W light bulb in your

house…– How much current is flowing

through the light bulb?

P=iV so i=P/V=40W/120V=0.33amps

– What is the resistance in the lightbulb?

V=iR so R=V/i=120V/0.33amps=360 ohmsor

P=V2/R so R=V2/P=(120V)2/40W=360 ohms

Electricity Basics

• What are materials that easily pass current?

• What are materials that do not easily allow current to flow?

• Can you give examples of each one?

Electricity Basics

• What are materials that easily pass current?– Conductors

• What are materials that do not easily allow current to flow?– Insulators

• Can you give examples of each one?– Conductor: copper, steel, etc.– Insulator: wood, glass, clay, etc.

Electric Circuits• A series circuit has the same

current flowing through all components– If one component fails then

current stops

• A parallel circuit has the same voltage drop across each component– If one component fails or is

disconnected it does not prevent the flow of current to other components

V

V

i

i3

i

i

i

i

i1 i2

i = i1 + i2 + i3

i

Electric Circuit - Problem• For the circuit to the right:

– Are the two resistors in series or in parallel? ___________

– What is the total resistance of the circuit? __________

– What is the current flowing through the circuit? ___________

– What is the power dissipated at the first element (I.e. the 360 ohm resistance – like a light bulb)? _______

– Do you think the circuits in your house are wired in series or parallel and why? ______________________________________________________________________

V120V

R= 360 ohms

R= 360 ohms

Electric Circuit - Problem• For the circuit to the right:

– Are the two resistors in series or in parallel? SERIES – each have same current flowing through them

– What is the total resistance of the circuit? 720 ohms – just add together

– What is the current flowing through the circuit? V=IR so I=V/R=120V/720ohms=0.166 amps

– What is the power dissipated at the first element (I.e. the 360 ohm resistance – like a light bulb)? P=I2R (since we know both of these) P=(.166amps)2x(720ohms)=20W

– Do you think the circuits in your house are wired in series or parallel and why? Parallel because (1) if in series than if one system stops working then current stops flowing and (2) the 120V system would provide varying power to light bulbs rated at the same power based on resistance – like this example, the “40W” light bulb (I.e. 360ohms) only “gives off” 20W (would be dimmer than hoped for)

V120V

R= 360 ohms

R= 360 ohms

Science on Vacation!

• Science helps you to learn how to describe what is going on around you!

• Think – Experiment – Observe– Just like you do with sports, friends, sledding,

reading, etc.

• Do not give up when you first do not understand something– Concentrate, draw a picture, propose a solution

Spring 2004 5th Grade Greenbriar West

Think, Experiment, Observe