A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s.As a result of the collision,the first ball moves at 50.0 cm/s,and the second ball stops.In what final direction does the first ball move?
A)in the x-direction
B)at an angle of 53.1 $\degree$ ccw from the x-direction
C)at an angle of 45.0 $\degree$ ccw from the x-direction
D)Such a collision cannot happen.

Question

Quizplus · Accepted Answer

Before the collision, there is only x and y motion. After the collision, the first ball (previously moving in the x-direction) gains some y-motion and the second ball (previously moving in the y-direction) gains some x-motion. Conservation of momentum and conservation of kinetic energy can be used to solve for the final velocities of the two balls. Applying trigonometry to these final velocities yields that the first ball moves at an angle of 53.1° counterclockwise from the x-direction. Therefore, the answer is B.

A Billiard Ball Is Moving in the X-Direction at 30 °\degree°

A Billiard Ball Is Moving in the X-Direction at 30 $\degree$