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A force is anything that can cause a change to objects. Forces can:
• change the shape of an object
• move or stop an object
• change the direction of a moving object.
A force can be classified as either a contact force or a non-contact force.
A contact force must touch or be in contact with an object to cause a change. Examples of contact forces are:
• the force that is used to push or pull things, like on a door to open or close it
• the force that a sculptor uses to turn clay into a pot
• the force of the wind to turn a windmill
A non-contact force does not have to touch an object to cause a change. Examples of noncontact forces are:
• the force due to gravity, like the Earth pulling the Moon towards itself
• the force due to electricity, like a proton and an electron attracting each other
• the force due to magnetism, like a magnet pulling a paper clip towards itself
The unit of force is the newton (symbol N). This unit is named after Sir Isaac Newton who first defined force. Force is a vector quantity and has a magnitude and a direction.
EFFECT OF FORCE:
1. Force can make a stationary body in motion. For example a football can be set to move by kicking it, i.e. by applying a force.
2. Force can stop a moving body – For example by applying brakes, a running cycle or a running vehicle can be stopped.
3. Force can change the direction of a moving object. For example; By applying force, i.e. by moving handle the direction of a running bicycle can be changed. Similarly by moving steering the direction of a running vehicle is changed.
4. Force can change the speed of a moving body – By accelerating, the speed of a running vehicle can be increased or by applying brakes the speed of a running vehicle can be decreased.
5. Force can change the shape and size of an object. For example -– By hammering, a block of metal can be turned into a thin sheet. By hammering a stone can be broken into pieces.
Forces are can also divided into two types:
1. Balanced Forces
2. Unbalanced Forces
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