What is momentum? Write its SI unit. Interpret force in terms of momentum. Represent the following graphically
(a) momentum versus velocity when mass is fixed.
(b) momentum versus mass when velocity is constant.
Sol.
Momentum is a vector quantity. It is defined for any moving body.
If a body of mass m is moving with velocity v, its momentum is defined as product of mass and velocity.
P = mv
The unit of momentum is kg m/s.
The direction of momentum will be the same as the direction of velocity.
Suppose a body of mass 1 kg is moving with 5m/s towards the north and another body of same mass is moving towards the south with the same velocity.
Their momentum will not be the same as they have a different direction.
The force is defined as the rate of change in momentum. If force is not applied on the body. its momentum will be conserved.
1st graph: If the mass is fixed, momentum increases linearly with velocity. The graph will be a straight line passing through the origin.
2nd graph: If velocity is fixed, momentum increases linearly with mass. The graph will be a straight line passing through the origin.