S2 Forces and Friction

S2 Forces and Friction

A force is a push or a pull

we cannot see forces but we can see their effects

A force can change an objects...

• speed

• direction

• shape

A force can be measured using a force meter.

The unit of force is the Newton, N. 

Multiple Choice

a force is a push or a pull

• true

• false

Multiple Choice

what is the unit for a force?

• Kilogram

• Newtons

• Joules

Multiple Choice

we can see forces but not their effects

• true

• false

Multiple Choice

which of the following is NOT an effect of a force?

• changed speed

• changed mass

• changed direction

• changed shape

Friction

is the force that occurs when two objects rub together

Friction changes kinetic energy into heat energy.

When objects move through air or water they encounter frictional forces which reduce their motion. This is known as drag.  

There are several ways to reduce friction:

• reduce the contact between surfaces

• reduce the force acting on an object

• Make the surfaces smoother.

•  Lubrication is another way to make a surface smoother.  

we could also make an object more streamlined

Multiple Choice

Who will experience more friction?

• A

• B

Multiple Choice

Where on a bike is friction helpful?

• brakes

• tyres

• bike frame

Multiple Choice

The energy change during friction is...

• Heat to kinetic

• kinetic to heat

• chemical to kinetic

• kinetic to chemical

Multiple Choice

Who is wanting to decrease friction?

Multiple Choice

which of the following will increase friction...

• reduce force on surface

• reduce contact between surfaces

• streamline the object

• make the surface rougher

Multiple Choice

which car is more streamlined?

• blue car

• green car