Question

State the Law of Conservation of Momentum? Give an example of a situation where momentum is conserved.

Answer 1

Momentum :

It is defined as the product of mass and velocity.

momentum $\underset{p}{\rightarrow}$ = m * $\underset{v}{\rightarrow}$

It is a vector quantity and is always directed in the direction of velocity.

Its units are kg m/sec

It always depends on mass and velocity.

conservation of momentum :

Total momentum of an isolated system before collision is always is equal to the total momentum after collision.

Explanation:

In a collision ,the momentum change of body 1 is equal to and opposite to the momentum change of body2.That is ,the momentum lost by the body1 is equal to the momentum gained by the body2.In most collisions between the two bodies,one body slows down and loses momentum while the other speeds up and gains the momentum.Yet , the total momentum of the two bodies ( body1 + body2) is the same before and after the collision.The total momentum of the system (collection of the two bodies) is conserved.

Consider two bodies of mass m1 and m2 moving initially with velocities u1 and u2.    Total momentum before collision = m1u1 + m2u2   Let after collision their velocities become v1 and v2 Total momentum after collision = m1v1 + m2v2 hence according to the law of conservation of momentum, m1u1 + m2u2 = m1v1+ m2v2 Example: In the game of pool, momentum is conserved; that is if one ball stops dead after the collision ,the other ball will continue away with all the momentum. If the moving ball continues or is deflected then the both balls will carry a portion of the momentum from the collision.