An object descends from a pulley.(adsbygoogle = window.adsbygoogle || []).push({});

http://img501.imageshack.us/img501/9783/physics12qm.th.jpg [Broken]

Use the conservation of mechanical energy to find the linear speed of the descending mass (m = 1.0kg) after it has descended a vertical distance of 2.0m from rest. (For the pulley, M = 0.30kg and R = 0.15m. Neglect friction and mass of the string)

I solved this question not using the conservation of mechanical energy. At first I tried using it though and I wound up getting:

v_{cm}= square root of (4/3 mgh/M)

However, I determined the acceleration using a pervious example:

a = 2mg/(2m + M)

and then used v^{2}= 2ax

and got 5.8m/s which is the right answer...

but I don't know how to solve this question using the conservation of mechanical energy.

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# Pulley with rotational consideration

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