Question

What object A collides with object B and bounces back its final momentum is?

Answer 1

Explanation : $p_f=-p_i$

Momentum of a body is defined as the product of its mass and velocity.

   i.e. $p=m\times v$

So, when an object is moving, it has momentum.

If $m_1$ and $m_2$ are the masses of objects A and B and $u_1\ and\ u_2$ are their initial velocities. so, their initial momentum will be:

$p_i=m_1u_1+m_2u_2$

If after collision it bounces back with same velocities, then final momentum becomes:

$p_f=-m_1u_1+(-m_2u_2)$

-ve sign shows that the motion is in opposite direction.

so, $p_f=-(m_1u_1+m_2u_2)$

or$p_f=-p_i$

Hence, its final momentum is in opposite direction of initial momentum.