1. The problem statement, all variables and given/known data The Q asks to show that the time rate of change in mechanical energy for a damped, undriven oscillator is dE/dt=-bV^2. 2. Relevant equations I assume you take the derivative of the total E eq, E=(1/2)mV^2 + (1/2)kx^2 but I'm unsure how to put the E eq into terms of t, like E(t). 3. The attempt at a solution Would you have to punch in the pos eq [x(t)=(Ae^(-βt))cos(ωt-δ)] in for x, then its derivative in for V? and then takes that entire eq's derivative? Seems like it would be too much work and not enough concept.