FORCE AND FRICTION

A force is

Anything which causes an object to accelerate

Unit

Newton (N)

It is measured using a

Spring balance or newton meter

Ex. (forces) (3)

A push or pull, weight (the pull of gravity), friction (a force between sliding surfaces)

Newtons 1st Law

An object will stay as it is unless a force causes it to change

Newtons 2nd Law

If an object experiences a force, it will move or change its velocity

The resulting acceleration is dependent on two things

The force being pulled, the mass of the object

In equation form, Newton’s 2nd Law is

F equals Ma (Force = Mass x Acceleration)

Newtons 3rd Law

For every force, there is an equal and opposite reaction

Contact & non-contact forces

Contact force

A force that touches an object to change its shape, speed or direction of movement

Non-contact force

A force that does not touch an object to change its shape, speed, or direction of movement

Magnets can be

Attracted and repelled by each other due to a magnetic force

Friction

A force that stops an object or causes it to slow down. It also generates heat

High friction

Car tyres on tarmac, rubber soled shoes on cement

Low friction

Car tyres on ice, steel on steel

Lubricants

Reduce friction by preventing direct contact of the two surfaces

Ex. (lubricants)

Oil and soap

Advantages

Can cause us to brake/slow down, helps us to hold things, helps us to move

Disadvantages

Causes wear (shoes, machinery, joints), generates unwanted heat

Weight is the

Force of gravity acting on an object’s mass

Mass is the

Amount of matter in an object