Work Theory Question

[DLxX]

Could you help me out with this question?

A woman swimming upstream is not moving with respect to the shore. Is she doing any work? If she stops swimming and merely floats, is work done on her?

[Sirus]

W=Fd\cos{\theta}

Distance can be defined relatively. Therefore, she is not doing any work with respect to the shore, but she is doing work with respect to the water (she travels a distance with respect to the water). Use this idea to answer the second question. What happens if she stops swimming?

[Clausius2]

Therefore, she is not doing any work with respect to the shore, but she is doing work with respect to the water (she travels a distance with respect to the water).

I don't really know what means to do work respect to something. The work is done, and is some amount of energy, respect to nothing. In both cases there is work done:

-In the first one, although the woman remains stationary respect to the shore, she is moving her arms, so that is doing a work over the water (that work is eventually transformed into internal energy and lately dissipated).

-In the second one, there is work done over the woman by the water, because there is a transferring of mechanical energy between the waves (I suppose there are waves in the sea :smile: ) and the woman.