00:01
Hello, here a block with a mass of 5 kilograms is released from point a and the track is frictionless except the portion from b to c.
00:13
First we have to calculate speed of the block at point b.
00:20
Potential energy at point a is completely converted to the kinetic energy at point b.
00:26
Therefore mg times h0, where h0 is 3 meters equals to m db squared over 2, then b equals to square root of 2, gh0, that is 2 2 times g, 0, which is 3 meters.
00:56
Let's calculate it.
01:12
That equals to 7 .667 meters per second.
01:21
Now let's move on and ask and solve question b.
01:25
Here we have to calculate coefficient of friction between the block and the rough surface.
01:32
So the initial potential energy wishes, which was at point a, was converted to the potential energy of reform spring, which is k times delta x squared over 2.
01:52
And delta x is 0 .2 meters.
01:57
And plus work for the friction force, which here we take as the absolute value.
02:04
So let's calculate this work.
02:57
That equals to 107 joules...