00:01
So the exercise asks when we throw two balls of the same mass on a wall, and one ball is made of clay and another is a rubber ball.
00:17
The exercise asks which one experiences the larger change in momentum.
00:25
Let's check first the rubber ball.
00:30
Let's say that this is the wall.
00:36
And a ball hit like this and it passes back.
00:47
So, at time, specifically at the point in time that it hits the wall, right before it hits the wall, let's say the momentum, the ball was pointing towards that direction right before, right after, right after, direction, direction of the moment points toward the other direction.
01:33
We can, okay, we basically assume inelastic collision, meaning the whole energy changes, it doesn't change.
01:48
It stays as a kinetic energy, the kinetic energy of the ball right before and right after collision with the wall.
01:58
The same.
02:00
And since, okay, from the definition of magnitude, which is just the mass times velocity, given that the energy doesn't change, kinetic energy doesn't change, therefore the velocity, the velocity right before and right after, that's exactly the same magnitude, velocity before, and velocity right after.
02:35
It's exactly the same.
02:37
But they have opposite directions.
02:41
Okay.
02:42
Therefore, delta p, change in momentum, which equals p after and p before.
02:59
Equals mass v after minus mass times v before.
03:12
And okay, these two have exactly the same, exactly the same...