Question
Thu May 24, 2012 By:
 

if force acting on a body is zero then its momentum is what

Expert Reply
Thu May 24, 2012
system momentum is always conserved and if the external forces of the system is zero
 

The second law states that the net force on a particle is equal to the time rate of change of its linear momentum p in an inertial reference frame:

where, since the law is valid only for constant-mass systems, the mass can be taken outside thedifferentiation operator by the constant factor rule in differentiation. Thus,

where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net force applied to a body produces a proportional acceleration. In other words, if a body is accelerating, then there is a force on it.

Any mass that is gained or lost by the system will cause a change in momentum that is not the result of an external force. A different equation is necessary for variable-mass systems (see below).

Consistent with the first law, the time derivative of the momentum is non-zero when the momentum changes direction, even if there is no change in its magnitude; such is the case with uniform circular motion. The relationship also implies the conservation of momentum: when the net force on the body is zero, the momentum of the body is constant. Any net force is equal to the rate of change of the momentum.


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