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. Pressure
2.1. A Force acting on an area
2.2. Pressure=Force/Area
2.3. S.I. unit for pressure is Pascal(Pa) or N/m2
3. Force
3.1. A Push or a Pull
3.2. S.I. unit for force is Newton(N)
3.3. Common Forces are Gravitational Force Magnetic Force Friction
3.4. Can be measured by a force-meter eg.An extension spring balance A compression spring balance
4. Kinds of forces
4.1. Gravitational Force
4.1.1. Gravitational Force is a force that pulls objects towards the Earth
4.1.2. It causes objects to have weight
4.1.3. The stronger the gravitational pull, the greater the weight of an object.
4.1.4. Weight=Mass*Gravitational Force
4.1.5. Gravitational Force of the Earth is 10N/kg.
4.2. Magnetic Force
4.2.1. Force between magnets.
4.2.2. Have two different poles North(S) & South(S).
4.2.3. Like poles repel & Unlike poles attract.
4.3. Frictional Force
4.3.1. A Force that exists when two objects are in contact.
4.3.2. Friction slows down the motion of object.
4.3.3. Ball bearings, wheels & applying lubricant helps reduce friction.
4.3.4. Friction can be a nuisance.
4.3.4.1. Eg. It causes wear-and-tear in an object or converts useful energy to heat which is unnecessary.
4.3.5. However,Friction is useful.
4.3.5.1. Eg. It prevents us from falling when we walk or run.