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!