- #1
Mr Davis 97
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Homework Statement
Solve the differential equation ##\displaystyle Cv^2 - mg = m\frac{d^2 y}{dt^2}##
Homework Equations
The Attempt at a Solution
The problem is nonlinear, so we need to use unconventional methods. Specifically, if we can express the derivative of y with respect to v, then we might be able to integrate in order to find y.
So ##\displaystyle \frac{dy}{dv} = \frac{dy}{dt}\frac{dt}{dv} = v \frac{dt}{dv} = \frac{v}{\frac{dv}{dt}}##
But ##\displaystyle \frac{dv}{dt}## is given by ##\displaystyle \frac{C}{m}v^2 - g##, so
##\displaystyle \frac{dy}{dv} = \frac{mv}{Cv^2 - mg}##
If we solve this, we get ##\displaystyle y = \frac{m}{2c} \ln{|1 - \frac{Cv^2}{mg}|}## where ##V_0 = 0##.
Is this the correct solution?