Forces - Chapter 28 - JC Science

Force

Anything that causes an object to move, speed up and down, change shape and go in a different direction

Examples of a force

A moving car

Unit of force

Newtons (N)

What is force measured with?

A newton meter in a lab

Calculating force

Force (N) = Mass (kg) × Acceleration (m/s²)

Balanced force

A force that moves an object with constant velocity and no change in its acceleration

Example of a balanced force

In a tug-of-war game when none of the teams are winning, the forces are balanced and the rope isn’t moving

Unbalanced force

A force that causes an object to accelerate (speed up and down)

Example of an unbalanced force

A car slows down or speeds up on a road

Contact force

Any force that must be in direct contact with the object it’s moving

Examples of contact forces

Pull, push, squeeze, stretch

Friction

When an object moves, friction is acting against it

→ It's a contact force

→ It's the force opposing motion

Example of friction

Car tyre moving on the road

Disadvantages of friction

1-Can be reduced by lubrication

2-Wears away machinery e.g. car tyre

Non-contact force

Any force that doesn’t need to touch the objects it’s moving

Example of a non-contact force

Magnets

Gravity

The closer a person is to a large mass e.g. a planet, the heavier their body will be as gravity pulls them closer towards the centre of the mass

→ Non-contact force

Gravitational acceleration

The force of gravity that causes objects to accelerate

Terminal velocity

The highest speed at which an object will fall through the air before the force of friction balances the force of gravity