Force

Force = Mass x Acceleration (F=ma)

Work is done only when an object is being moved.

To moved things, we can pull or push (apply force).

Forces can be seen but their effects can be seen and felt.

A force can be seen when:

v A stationary objects moves

v A moving object moves faster

v A moving object changes direction

v A moving objects stops

v The object changes its shape.

Balanced forces do not cause a change in motion.

Gravitational Force

v Is the pull of gravity

v Measured by weight

v Decrease with increasing distance from the centre of the Earth.

v The higher the object is from the ground the more gravitational potential energy.

v The larger the mass, the greater the gravitational force.

v Acts from a distance.

Frictional Force

v Produced when two things rub each other.

v Acts in the opposite direction

v The rougher the surface, the more friction it has.

v The heavier the mass, the greater the friction.

v Advantages: Prevent us from falling.

v Disadvantages: Cause wear and tear and heat – waste energy.

v Use lubricants, rollers and ball bearings to reduce friction.

Elastic Spring Force

v When an object is acted upon by a force, it can be compressed, stretched or bend.

v If the object returns to its original shape after the force is removed, it is said to be elastic.

v Found in rubber band and spring.

Take note of the graph that comes with the question.

The graph above measures the extension – so it starts from 0cm. It did not mention the length of the original spring.

The graph below measure the length of the entire spring – so it does not start from 0cm.

The heavier the mass, the longer the extension. The extension will be constant until it comes to a point where the spring cannot return to its original length.

Magnetic Force

• Magnetism is the attractive or repulsive force that acts between magnetic materials
• Can pass through non-magnetic substances
• Can act from a distance