When a ball rolls down a cliff, it gains momentum. When a car speeds up on a racing track, it gains momentum. In both cases, the velocity of the object is changing.

Momentum is often described as mass times velocity of a particle. In everyday cases, mass stays constant for any given object. Hence, when velocity changes, so does momentum.

**Momentum = Mass x Velocity**

Momentum is important, because it turns out that it is related to the force applied on the particle, as:

i.e. force on a particle is equal to the rate of change of its momentum. If you assume the mass to be constant, you get:

Since dv/dt or the rate of change of velocity is just acceleration a, you can write

This is Newton’s Second law of motion and works really well in the domain of Newtonian Mechanics.

A very important property of momentum is that, given there are no external forces on a body, its momentum is conserved. This property is known as the “law of conservation of momentum” and is never violated.

*What we have discussed above is the linear momentum. There is yet another form of momentum, called the Angular Momentum which has a conservation law of its own.*

*Related*

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