# Theoretical angular momentum problems

1. Feb 25, 2009

### nns91

1. The problem statement, all variables and given/known data

1. Folk wisdom says that a cat always lands on its feet. If a cat starts falling with its feet up, how can it land on its feet without violating the law of conservation of angular momentum ?

2. Is it easier to crawl radially outward or radially inward on a rotating merry-go-round ? Why ?

2. Relevant equations

Conservation of angular momentum:

3. The attempt at a solution

1. I think by spinning around its center of mass but I am not sure. What do you guys think ?

2. I guess this one has to deal with conservation of angular momentum but I don't know how to start it. Any hint ??

2. Feb 25, 2009

### Nabeshin

1. To spin would be to change the angular momentum, so how can the cat reorient itself so that $$\Delta L=0$$?

2. Consider that you know angular momentum must be conserved in all cases, but energy need not be. What happens to the total energy when someone moves radially closer or farther away?

3. Feb 25, 2009

### nns91

2. Kinetic energy will increase when the radius is shorter. So it means it is easier to crawl outside ??

4. Feb 25, 2009

### Nabeshin

Right-o, you have to do work to decrease your radius, and work is done on you to increase your radius. How about the first one? Any thoughts?

5. Feb 25, 2009

### nns91

I cannot think of anything yet. Any hint ?

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