00:03
In this problem we have a bullet flying towards a block which is at rest on the floor and then we're told it travels for a distance of 1 .3 meters after they have collided and stuck together.
00:19
So the first part we want to know what was the initial velocity of the bullet and so we have a collision taking place.
00:25
This is conservation momentum so i'm gonna put this is object one and this is object two.
00:30
So the mass of object one that little bullet is 0 .012 kilograms and the block is going to be six kilograms.
00:39
Initially this block is at rest and so its velocity is zero.
00:43
We don't know the initial velocity of the bullet that's what we're looking for but we know after they collide and stick together they're going to move off with the final velocity of 1 .7 meters per second.
00:59
Okay so we're going to do our conservation momentum so we have momentum of object one initially plus the momentum of object two initially is equal to both their momentums after the fact.
01:15
So we know initially there is no momentum for the block because it is at rest.
01:19
So let's plug in our values so we have mass of object one times initial velocity is equal to and we can factor out one of these masses because now they're moving as a singular object and so we're simply going to treat them like one object and add their masses.
01:41
It would be the same thing if you left them separate and then added those two after the fact so you could do it either way.
01:50
All right so when we do our calculations right here we get 10 .22 and you're going to take both sides and divide it by that 0 .012 and we get 851 .7 so we put 852 meters per second as the initial velocity of that ball is moving very very quickly...