Question

Using the

principle of momentum conservation, explain what happenswhen a
moving billiard ball collides with a stationary ball (cueball
hitting the eight ball).

Answer 1

The principle of momentum conservation states that if there no external force the total momentum of the system before and after the collision is conserved.

Since momentum is a vector, we should investigate the directions and magnitudes of initial and final momentum.

`\vec{P}_(initial) = \vec{P}_(final)\\\vec{P}_(initial) = m_1\vec{v}_1 + 0\\\vec{P}_(final) = m_1\vec{v}_1' + m_2 \vec{v}_2'`

If the first ball hits the second ball with an angle, we should separate the x- and y-components of the momentum (or velocity), and apply conservation of momentum separately on x- and y-directions.