- #1

joej24

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## Homework Statement

(a) If R = 12 cm, M = 570 g, and m = 50 g in Figure 10-18 (below), find the speed of the block after it has descended 50 cm starting from rest. Solve the problem using energy conservation principles.

M is the mass of the mounted uniform disk.

A block with mass m hangs from a massless cord that is wrapped around the rim of the disk. The cord does not slip, and there is no friction at the axle.

(b) Repeat (a) with R = 5.0 cm.

## Homework Equations

F = ma

alpha * R = a

torque = I * alpha

U+K = U+K

## The Attempt at a Solution

I understood how to solve this problem (#9) with kinematics ( solving for acceleration and then using v^2 = vnot^2 + 2ad) but am having trouble with using conservation of energy.

This was my attempt

U + K = U + K

//It is initially at rest

0 + 0 = -mgh + Krotational + Ktangential

mgh = 05*I*omega + 0.5mv

I = 0.5mr = .004104 kg * m

a = 1.4626 so alpha = 12.189 rad/s

I don't think my initial setup is correct though because I do not get the correct answer

If someone could show me how I can post the image up here that'd be great too

Thanks!