00:01
Okay, here we have two pendula, one that is starting at a height h above the other, which is at rest at the equilibrium.
00:09
They have both the same length of 50 centimeters, m1, which is the one that is h above m2.
00:15
It weighs 2 kilograms, m2 is 3 kilograms, and the height difference is 10 centimeters or 0 .1 meters.
00:21
The frequency of any pendulum going through a small angle is 1 over 2 pi times a square root of g over l.
00:29
In this case, l is 50 centimeters or 0 .5 meters.
00:34
We get 0 .7 hertz.
00:38
Okay, so that's the easy part.
00:40
That's part a.
00:40
For part b, we need to start off with some energy conservation to figure out how fast one is when it strikes two.
00:49
So we know that m1gh equals one half m1 v1 squared.
00:59
The ms cancel out.
01:02
And we get that v1 equals square root of 2gh equals 1 .4 meters per second.
01:23
All right.
01:24
Now we need to use momentum conservation to figure out the mass is the mass of the combined, sorry, the speed of the combined masses after collision...