1. Effects of Forces
1.1. Start an object moving or stop a moving object
1.2. Speed up or slow down a moving object
1.3. Change the direction of a moving object
1.4. Change the shape or size of an object
2. Force
2.1. A Push or a Pull
2.2. S.I. unit for force is Newton(N)
2.3. Common Forces are Gravitational Force Magnetic Force Friction
2.4. Can be measured by a force-meter eg.An extension spring balance A compression spring balance
3. Kinds of forces
3.1. Gravitational Force
3.1.1. Gravitational Force is a force that pulls objects towards the Earth
3.1.2. It causes objects to have weight
3.1.3. The stronger the gravitational pull, the greater the weight of an object.
3.1.4. Weight=Mass*Gravitational Force
3.1.5. Gravitational Force of the Earth is 10N/kg.
3.2. Magnetic Force
3.2.1. Force between magnets.
3.2.2. Have two different poles North(S) & South(S).
3.2.3. Like poles repel & Unlike poles attract.
3.3. Frictional Force
3.3.1. A Force that exists when two objects are in contact.
3.3.2. Friction slows down the motion of object.
3.3.3. Ball bearings, wheels & applying lubricant helps reduce friction.
3.3.4. Friction can be a nuisance.
3.3.4.1. Eg. It causes wear-and-tear in an object or converts useful energy to heat which is unnecessary.
3.3.5. However,Friction is useful.
3.3.5.1. Eg. It prevents us from falling when we walk or run.