Frictionless Floor Multiple Choice

[kajasu88]

Homework Statement

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.

 

[berkeman]

Homework Statement

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.

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.

 

[rock.freak667]

Any thoughts about it?

 

[kajasu88]

I don't think it has to do with pushing on the floor because if there is no friction, that wouldn't work right? unless they pushed up, but that wouldn't make him go forward.
so spit...
thats all i can htink of right now

 

[berkeman]

I don't think it has to do with pushing on the floor because if there is no friction, that wouldn't work right? unless they pushed up, but that wouldn't make him go forward.
so spit...
thats all i can htink of right now

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

 

[rock.freak667]

I don't think it has to do with pushing on the floor because if there is no friction, that wouldn't work right? unless they pushed up, but that wouldn't make him go forward.
so spit...
thats all i can htink of right now

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

 

[kajasu88]

well it has to be conservation of momentum... don't 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?

 

[Jebus_Chris]

Yes, it's c.

$$m_1v_1=m_2v_2$$