00:01
So in this question, we have two balls.
00:03
Ball a and ball b.
00:04
They're moving at each other at right angle.
00:08
And we know that they are of equal mass, so they are both of mass m, and they move with each other with velocity b and va.
00:17
After the collision, b moves straight up, and we do not know how ball a will move.
00:24
So we know this is the x direction, and this is the y direction.
00:30
And we know it's the elastic collision.
00:33
So let's first try to assume what a will try to move.
00:41
Let's assume that maybe a moves this way, and we'll call it va prime, this is vb prime.
00:49
And we can write down the conservation of momentum.
00:52
And since this is elastic, we also have as conservation of kinetic energy.
00:56
We need to find both the direction and the velocity of the two balls after the collision.
01:02
So that means we need to find vb prime.
01:06
And we also need to find v -a prime and the angle it has.
01:13
So, or in other words, another way of writing it is we can find the two components of va.
01:20
So v -a prime is x component, it's x component and it's y component.
01:26
And i personally find that to be a lot easier because then we don't have to do with sine and cosine.
01:36
So this is just two components of it.
01:41
Then let's look at the conservation loss we have.
01:45
We have conservation loss in the x direction.
01:48
So we have m vb.
01:52
This is the momentum before the collision equals m va x prime.
01:59
So this is after the collision.
02:00
Since b is moving vertically, it has no horizontal components.
02:04
What about the y direction? before the collision, we have mva.
02:08
After the collision, we have nvay y prime plus mvb prime.
02:17
So both a and b will contribute to the y direction.
02:21
We also have the conservation of kinetic energy...