P2 2.1 Forces Between objects

When two objects interact (push or pull), they exert equal and opposite

forces on each other.

What happens?

10N 10N

P2 2.1 Forces Between objects

When two objects interact (push or pull), they exert equal and opposite

forces on each other.

The skaters move towards each other

What happens?

10N 10N

P2 2.1 Forces Between objects

At any stage this is true

But to pull the car out of the mud

Ft > F c

Ft F c

Friction acts where the tyre is in contact with the road.

(even when accelerating or braking)

What happens if there isn’t

enough friction ?

Wheel slides

What happens if a car accelerates while its wheels are on carpet mats?

Carpet mats move backwards, car moves forwards (a little)

5 N

1 Kg

Ft FtFr Fr

What would happen if the trolley got stuck on the runway?

You pull the runway along too!

5 N

Trolley pulled along a flat runway

(Not showing vertical forces)

Friction on the trolley

Friction on the runway

Pull on the trolley

Pull on the person pulling

A floating ball

A

D

C

B

Equal and opposite forces:* act on different objects* act in opposite directions* are the same type of force* act along the same line

B - weight (force of gravity on the ball)A - gravitational pull of ball on the earth

C - contact force of water on ball (Upthrust)A - contact force of ball on the water

A floating ball

N S

Paper clips held by a magnet

A

D

C

B

E

F

HG

Equal and opposite forces:* act on different objects* act in opposite directions* are the same type of force* act along the same line

A book at rest A stretched spring

P Q R S

X

Y

U

V

• Friction is a contact force between surfaces.• The unit of force is the newton (N).