# Diving board physics problem

1. Jun 30, 2008

### Vikingjl11

1. The problem statement, all variables and given/known data
After jumping up and down on a diving board, Roger jumps off the diving board. Hakim claims that Roger does work on the diving board because he supplies energy to it. Ludmilla claims that the diving board does work on Roger and supplies energy to him. Which one, if either, is correct?

a.Hakim, because the diving board is deformed and vibrated like a spring when Roger jumps.
b.Ludmilla, because Roger jumps up in the air above the diving board.
c.Neither, because Roger's muscles do all the work.
d.Both, because Roger's muscles do all the work.
e.Neither, because the diving board does all the work.

2. The attempt at a solution

I believe that both the board and Roger do work, but the answer which satisfies that conclusion also states that Roger's muscles do all the work. This has left me somewhat flummoxed. Can anyone elucidate? Thanks.

2. Jun 30, 2008

### calef

Re: Work

I think (A) is correct, because Roger is the only external force in this problem. Without Roger, the diving board would not be deformed at all, and Roger's kinetic energy is only really changing because of what he did.

The tricky wording here kind of gives it away: Ludmilla's claim doesn't make sense: How is the diving board supplying energy to Roger? It isn't supplying anything. It's only redirecting Roger's input.

3. Jun 30, 2008

### Vikingjl11

Re: Work

Yea, your explanation certainly makes sense. Thanks for the insight.