A light rigid rod of length L has a mass m attached to its end, forming a simple pendulum. It is inverted and then released (I don't know what that's supposed to mean). What are:
a) the speed v at its lowest point
b) the tension T in the suspension at that instant
The Attempt at a Solution
at the beginning, when it is dropped down, we should have K = 0 and U = mgL
at the bottom when it is finished dropping, we should have K = 1/2mv^2 U = 0
1/2 mv^2 = mgl
v = sqrt(2gL)
but the book says 2sqrt(gl)...
what did I do wrong?