Newton's Second law of Motion

Newton's first law of motion deals with the behaviour of objects on which all existing forces are balanced. Also, it is clear from the first law of motion that a body in motion needs a force to change the direction of motion or the magnitude of velocity or both. This implies that force is such a physical quantity that causes or tends to cause an acceleration.

Newton's second law of motion deals with the behaviour of objects on which all existing forces are not balanced. According to this law, the rate of change of momentum of a body is directly proportional to the external force applied on it and the change in momentum takes place in the direction of the force.

The force acting on a body is measured by the product of mass of the body and acceleration produced by the force acting on the body. The second law of motion gives us a measure of the force.

F = ma

The acceleration produced in the body depends upon the inertia of the body (i.e) greater the inertia, lesser the acceleration. One newton is defined as that force which, when acting on unit mass produces unit acceleration. Force is a vector quantity. The unit of force is kgm s^-2 or newton. Its dimensional formula is MLT^-2.

Impulse

Impulse = final momentum of the body - initial momentum of the body. (i.e) Impulse of the force = Change in momentum

The above equation shows that the total change in the momentum of a body during a time interval is equal to the impulse of the force acting during the same interval of time. This is called principle of impulse and momentum.

 Examples

A person falling on a cemented floor gets injured more where as a person falling on a sand floor does not get hurt. For the same reason, in wrestling, high jump etc., soft ground is provided.