General

What is linear momentum?

Momentum ($p$) is the product of an object's mass and velocity:

$$p = mv$$ (64.1)

Where $p$ is momentum in kilogram-meters per second (kg$\cdot \ m/s$), $m$ is the mass of the object in kilograms (kg), and $v$ is the velocity in meters per second ($m/s$).

How can $p$ be incorporated into Newton's second law of motion?

$$\Sigma F = ma = m \ \frac{\Delta v}{\Delta t} = \frac{m\left... ...t} = \frac{mv - mv_{o}}{\Delta t} = \frac{\Delta p}{\Delta t}$$ (64.2)

$$\Sigma F = \frac{\Delta p}{\Delta t}$$ (64.3)

What is the law of conservation of momentum?

Law 9   The total momentum of an isolated system of bodies remains constant.

This is an application of the conservation of energy and explains why the momenta before and after a collision are equal. That is not to say that the momentum for each object can not change, but the overall total momentum will be conserved before and after the collision.