00:01
Hockey puck on ice, and it's going to travel a distance of 36 meters before it comes to a rest.
00:07
So its final speed is zero, and it's initially traveling at 8 .7 meters per second.
00:13
And we want to know what is the coefficient of friction that causes this slowdown.
00:17
And so this equation will be work is equal to the change in kinetic energy.
00:23
Work is force times distance, and change is final minus initial.
00:32
And at first, it looks like we don't have everything we need to solve for this problem, but we do.
00:37
And so let's figure out what force is bringing this to a stop.
00:40
The only force that's acting on this puck as it's sliding is the force of friction.
00:45
And we know the final velocity of zero, so this will simply be zero.
00:53
And so now let's look at force of friction.
00:55
We don't know force of friction, but we can solve for it because this is on a horizontal ground.
01:01
Let's draw a free body diagram.
01:02
We have force of gravity going down and normal force going up.
01:07
It is moving only in the horizontal.
01:10
It is at equilibrium in the vertical.
01:13
And so that means normal force is going to be equal to the magnitude of force of gravity...