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Laws of Motion
Introduction:
To start something moving one has to either pull it or push it. A body is said to be pushed if a person applies a force on it and its direction of motion is away from the person. For example, a nil is pushed into wall. A body is said to be pulled, if a force is applied on it by a person or object and its direction of motion is towards the person or object. For example, a nail is pulled out of wall. Pushes and pulls are the examples of forces.Weight is a common force of attraction exerted by the Earth on the body. Gravity pulls every thing on the Earth towards its centre. If we take an object to the Moon, the weight of the object will be 1/6 th of its weight on the Earth because the Moon has a weaker gravitational field than the Earth. Objects which are far from planets in space are weightless, but their masses remain the same.
Force is thus defined as a push or a pull which produces or tends to produce a change in the state of rest or of uniform motion of a body. An object at rest can not by itself change its state of rest unless an external force is applied on it, for example, we may push it or pull it or to change its state of rest. Similarly if an object is in motion, we have to destroy its motion and bright it to rest.
Force is not only the push or a pull of muscular force. It includes all such as gravitational attraction, electrical forces, electromagnetic forces, nuclear forces and so on which could cause many short of motion on a body. For example; force of gravitational attraction causes a body to fall freely from a given height. To keep a body moving at a uniform speed, a constant force throughout the duration of motion has to be applied.
