# Thread: laplace transform of a derivative

1. ## laplace transform of a derivative

how do you take the laplace transform of this equation:
I*x''+b*x'-b*y'+k*x-k*y=Mc+Md

I, B, and x are variables, assuming Mc and Md are as well since they are for the motor inertia

2. Originally Posted by jlynn36
how do you take the laplace transform of this equation:
I*x''+b*x'-b*y'+k*x-k*y=Mc+Md

I, B, and x are variables, assuming Mc and Md are as well since they are for the motor inertia
If you are expected to be able to do a problem like this, then you are expected to have learned that
$L(dy/dx)= y(0)+ sL(y)$

You can get that, and the second derivative, by integrating
$\int_0^\infty e^{-st}\frac{dy}{dt} dt$
by parts.