A billiard ball moving at 6.00 m/s strikes a stationary ball of the same mass. after the collision, the first ball moves at 5.39 m/s at an angle of 26.0° with respect to the original line of motion. assuming an elastic collision (and ignoring friction and rotational motion), find the struck ball's velocity after the collision.

Question

Physics

Emmanuel Buckley

6 April, 17:13

A billiard ball moving at 6.00 m/s strikes a stationary ball of the same mass. after the collision, the first ball moves at 5.39 m/s at an angle of 26.0° with respect to the original line of motion. assuming an elastic collision (and ignoring friction and rotational motion), find the struck ball's velocity after the collision.

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Answers (1)

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Kelvin Lucas · Answer 1

To do this question, we need to know that momentum is conserved, meaning the overall velocity of the two balls has to be the same before and after the collision.

After collision ...

Ball 1: 4.33m/s * cos 30 = 3.75 m/s (x-component)

4.33m/s * sin 30 = 2.165 m/s (y-component)

Ball 2 (struck ball) : 5 m/s - 3.75m/s = 1.25 m/s (x-component)

-2.165 m/s (y-component) note: it has to be in the opposite direction to conserve momentum

tan-1 (2.165/1.25) = 60 degrees

Struck ball's velocity = sqrt (1.25^2 + 2.165^2) = 2.5 m/s at 60 degree with respect to the original line of motion.

Hope you understand!