Principle of Work and Energy: Spring and Mass

[Peter P.]

Homework Statement

When the 65-kg cylinder is released from rest, the spring is subjected to a tension of 75. Determine the speed of the cylinder after it has fallen 300. How far has it fallen when it momentarily stops?

Given Diagram:

Homework Equations

The Attempt at a Solution

I started with a displacement equation. When the mass has fallen 300 mm (or 0.3 m), the string should stretch 0.6 m. I think that i can use F = kx, where F = T. So then the spring is already stretched by 0.25 m. From the free body diagram of the cylinder, i know that there will be potential gravitational energy, and a tension force acting in the opposite direction. Heres my long shot, but can i make the tension be represented by the potential energy of the spring (V_s = 0.5ks²). Then i get a little lost in whether or not i can do that.

Thanks in advance for any help.

 

[ehild]

Hi PeterP,

you are on the right track, go ahead. ehild