# Frictionless Floor Multiple Choice

1. Sep 1, 2009

### kajasu88

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

Somehow Larry got stuck in the middle of a room with a frictionless floor. Larry is at rest. How could Larry start moving to get to the edge of the room?

A. Push on the floor with his hands or feet. That way the floor could exert a force on him and Larry could accelerate from rest to moving linearly.

B. Push on the floor with his hands or feet. That way the floor could exert a torque on him and Larry could accelerate from rest to rotating.

C. Spit. It's gross, but since momentum is conserved, Larry could gain an the same amount of momentum as the initial momentum of his spit.

D. Spit. It's gross, but since force is conserved, Larry could accelerate.

E. Spit. It's gross, but since momentum is conserved, Larry would have the same speed as his spit.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 1, 2009

### Staff: Mentor

So you stated the problem. What do you think the answer is and why? We don't do your homework/coursework for you here at the PF.

3. Sep 1, 2009

4. Sep 3, 2009

### kajasu88

I dont think it has to do with pushing on the floor because if there is no friction, that wouldnt work right? unless they pushed up, but that wouldnt make him go forward.
so spit...
thats all i can htink of right now

5. Sep 3, 2009

### Staff: Mentor

Spitting is part of the right answer. Now which of the 3 spitting choices is correct?

6. Sep 3, 2009

### rock.freak667

So what about the spit? There are only 3 left to choose from. Which one do you think it is and why?

7. Sep 3, 2009

### kajasu88

well it has to be conservation of momentum... dont know about conservation of force....
and has to be c because e would mean that the spit and larry have the same mass.

so C?

8. Sep 3, 2009

### Jebus_Chris

Yes, it's c.

$$m_1v_1=m_2v_2$$