- #1
rolypoly3000
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1. We have a cylinder of Mass M rotating about its axis. String is wound around it. Other end is connected to a spring. A mass m is attached to the spring.
The problem is to find the Lagrangian. My only issue is with finding the potential energy. The problem asks to use the distance of the mass m from center of axis of cylinder to be 'y' and length of spring to be 's'.
If I take downward positive, I can write,( with U=0 at axis of cylinder) I can write,
U=mgy + 1/2ks^2
But if I take downward negative, U= -mgy+1/2 k s^2
So using two coordinate systems will result in two different end answers for equations of motion.
Any thing wrong in what I am doing
The problem is to find the Lagrangian. My only issue is with finding the potential energy. The problem asks to use the distance of the mass m from center of axis of cylinder to be 'y' and length of spring to be 's'.
If I take downward positive, I can write,( with U=0 at axis of cylinder) I can write,
U=mgy + 1/2ks^2
But if I take downward negative, U= -mgy+1/2 k s^2
So using two coordinate systems will result in two different end answers for equations of motion.
Any thing wrong in what I am doing