00:04
In this problem, we have a ball that hits a wall, and it bounces against the wall and returns going the opposite direction at the same speed that it hit the wall with.
00:17
We're asked to calculate what is the change in a ball's kinetic energy.
00:22
And the word i want to emphasize here is change.
00:24
We're not as to calculate the initial or the final kinetic energy, but rather what is the change before and after the collision.
00:34
So let's do a little bit of analysis here before we dive into calculation.
00:40
Look at the formula for kinetic energy.
00:43
One half times mass times velocity squared.
00:46
The only two things that affect an object's kinetic energy are its mass and its velocity.
00:55
If we analyze the ball before the collision and after the collision, let's see if we actually find any change.
01:05
What was the mass before the collision? well, it's 0 .1 kilograms.
01:09
What was the mass after the collision? it's still 0 .1 kilograms.
01:15
No change there, so i don't have to worry about it.
01:18
What was the velocity before the collision? two meters per second.
01:24
What's the velocity after the collision? two meters per second...