# Elastic collision in 2-d.

## Homework Statement

Consider an elastic collision (ignoring friction and rotational motion). A queue ball initially moving at 2.9 m/s strikes a stationary eight ball of the same size and mass. After the collision, the queue ball’s final speed is 1 m/s. Find the queue ball’s angle with respect to its original line of motion.

## Homework Equations

I can't seem to figure out how you're supposed to get an angle for this, if none is given.

## The Attempt at a Solution

in 1-d the equation would be something like m1v1+m2v2=(m1+m2)*V. In 2-d, I assume you need a trig function, but how is that useful with no given angle?

tiny-tim
Homework Helper
Welcome to PF!

Hi LTZach ! Welcome to PF! Consider an elastic collision (ignoring friction and rotational motion). A queue ball initially moving at 2.9 m/s strikes a stationary eight ball of the same size and mass. After the collision, the queue ball’s final speed is 1 m/s. Find the queue ball’s angle with respect to its original line of motion.
(btw, it's a cue ball! )
What do you get? 