# Stuck with a problem from a take home test

1. Mar 15, 2005

### joselyn

A body free fall into a viscous fluid. Calculate the dissipating speed of kinetic and potential energy during this motion into the fluid. ( suppose Yo initial height)

2. Mar 16, 2005

### HallsofIvy

Staff Emeritus
Well, you can't do that if you are given no numerical values! What are you given? The potential energy is, of course, mgh where h is the height of the body. kinetic energy is (1/2)mv2. If there were no dissipation (no viscous fluid) the sum of those (total energy) would be constant. I presume that the "dissapating speed" is the rate at which that sum is decreasing.

3. Mar 16, 2005

### xanthym

For instance, are you concerned with Aerodynamic Drag ("air resistance") and/or Terminal Velocity?? If so, what Reynold's Number range are you considering??