(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

2 boxes are connected by a massless rope. the system is frictionless

m_{1}= 3kg

m_{2}= 5kg

http://img388.imageshack.us/img388/2033/problemwr4.jpg [Broken]

Find m_{1}'s speed when it is 1.8 m above the ground.

2. Relevant equations

K = 0.5mv^2

U = mg delta y

3. The attempt at a solution

v_{1}=v_{2}obviously

also, delta y of m_{1}= 1.8, whereas delta y of m_{2}=-1.8

At the beginning:

Etot = K_{1}+ K_{2}+ U_{1}+ U_{2}

since K_{1}, K_{2}and U_{1}are = 0, Etot = U_{2}= m_{2}*g*5 = 25g

When m_{1}is 1.8 meters above the ground:

Etot = K_{1}+K_{2}+U_{1}+U_{2}

25g = 0.5m_{1}v^{2}+0.5m_{2}v^{2}+1.8m_{1}g-1.8m_{2}g

solving for v gives 8.37,

but the answer is 2.97

can anyone help me find what is wrong in my reasoning?

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# Homework Help: Conservation of energy theorem problem

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