Is This a Conservation of Angular Momentum Problem?

AI Thread Summary
The discussion revolves around a physics problem involving two people on a board balanced on a fulcrum, specifically addressing the conservation of angular momentum. When the lighter person jumps straight up at 1.5 m/s, the total angular momentum of the system must remain conserved, starting and ending at zero. The key equation m_1 r_1 v_1 = m_2 r_2 v_2 is highlighted to determine the speed of the heavier person after the jump. It is emphasized that the board's mass can be ignored due to its lightness, allowing focus on the two individuals' contributions to angular momentum. Understanding the orientation of angular momentum is crucial for solving the problem accurately.
Kchu
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i don't know how to solve this problem is it a conservation of momentum problem?

because can't you just use

mv=mv?
 

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What exactly is the problem?
 
oops! =]

**Two people are standing on a very light board that is balanced on a fulcrum. The lighter person suddenly jumps straight up at 1.5m/s
Just after he jumps, how fast will the heavier person be moving?**
 
Consider conservation of angular momentum.
 
mrv=mrv but it doesn't rotate?
 
Assuming you mean that to be m_1 r_1 v_1 = m_2 r_2 v_2, then that is correct. What makes you think it doesn't rotate? (If the board doesn't rotate, the second man would have speed = 0.)

A bit more explanation may help.

The total angular momentum of the system about the fulcrum is conserved. It starts out at zero before the man jumps and remains at zero after the man jumps. The system consists of both men and the board. (Since the board is light, we can ignore its mass and angular momentum.)

What is the angular momentum of the man after he jumps? Then what must be the angular momentum of the other man? (Don't forget that angular momentum has an orientation; think clockwise versus counterclockwise.) Use that to figure out the second man's speed.
 

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