FORCESFORCESOutcome

4.6Stage 4

overview1) What is a force?

• Examples of forces• Measuring forces

2) Contact forces3) Non-contact forces4) Balanced Forces5) Unbalanced Forces

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what is a force?

Nothing moves by itself. Objects must be

pushed or pulled!

…or a…

A force is a…

We use forces every day!

Action Push and/or Pull?Pressing a button

Climbing a tree

Jumping

Walking

Towing a car

Jumping

PUSH

PULL

PUSH

PUSH

PULL

PUSH

PUSH & PULL

PULL

PUSH

What changes happen when forces are applied?

Changing

the speed

of an

object

Changing the shape of an object

Stopping a moving object

Changing

the

direction of

an object

Moving a stationary object

•Forces are measured in Newtons, written as N for short

How do we measure a force?

http://www.cowetaschools.org/eses/IT/Clipart%20for%20Forces%20and%20Motion%20WebQuest/force%20meter.gif

•Forces are measured using a Force Meter, which uses a spring

•The bigger the force, the more the spring stretches

•Or, we can calculate it using this equation: Force = mass x acceleration

Forces can happen between objects………...

…or from a distance

(non-contactnon-contact forces):

1)Electrostatic force

2) Magnetic force

3) Gravitational force

…by touching(contactcontact

forces):• Frictional

force

Forces normally occur in pairs………

These pairs are called Action and Reaction

• The Action force causes a change

Example: car tyres push backwards on the road to move the car forwards

• The Reaction force is the force that ‘reacts’ to the action force.

Example: the road pushes forward against the cars tyres

Forces normally occur in pairs………

Action and Reaction forces act in OPPOSITE directions

They can be BALANCED or they can be

UNBALANCED