Calculating Energy Dissipation in Free Fall with Drag Force

[impendingChaos]

Homework Statement

Need to energy dissipation by the drap force on a ball in free fall from height h and when it has reached terminal speed, assuming it happens before it hits thr ground. Drag force has magnitude bv^2, where b is drag coefficient and v is instantaneous speed of the ball.

Homework Equations

I have calculated in an earlier part of the problem that terminal velocity:
Vt=root(mg/b)

Also, isn't the energy dissipation equation:
Ediss=mgh

The Attempt at a Solution

I have the above equations but am unclear where to move next.

 

[denverdoc]

Not sure what you mean by Ediss=mgh. If chosing conservation of energy, one could simply assume that the drag energy(work) is the difference between the final and initial sums of PE and KE. The problem I see, is that the eqn you posted for Vt says nothing about height.

In other words if we knew the distance required to reach terminal velocity, you're home free.

 

[impendingChaos]

Ok will check that, Ediss is Energy dissipated

thx!

 

[denverdoc]

no sweat, either way problem is soluble:

mv'=-b*v^2+mg.