# Biophysics Problem 17

In a normal joint, the coefficient of friction is approximately 0.003. In arthritic patients, the value of this coefficient can be considerably larger because of changes in the lubricating fluid. Assuming all other things equal, how much more energy is dissipated in an arthritic joint where $\mathrm{\mu = 0.03}$ than in a normal joint?

#### First Step

This problem is not involved. Some students have had trouble with it because they didn't think it could be so easy.

If the coefficient of friction is 10 times as big the frictional forces will be 10 times as big. Consequently, the work to overcome friction will be 10 times as big and 10 times as much energy will be required.

That's all there is to it.