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

Two boxes are connected over a pulley and hel AT REST. Box A has a mass of 15kg and box B has a mass of 12kg. If the bottom of box A is originally 85cm above the floor, with what speed will it contact the floor when the system is released? Use conservation of energy and assume that friction is negligible. (Hint: Think abou the total energy of the system before and after the block A is released)

2. Relevant equations

ET= mgh + 1/2mv squared

Ek=1/2mv squared

Ep=mgh

3. The attempt at a solution

Before released: Eta= (15)(9.8)(.85)

Eta= 124.95J

After released: Etb= mgh

Etb= 12(9.8)(.85)

up to this point, the test says I have it write (as seen from the teachers marking)

then this is where i somehow went wrong: 124.95-99.96= Change in Energy

*at this point, the marker said, "B HAS Ek TOO!"

then i did: 24.99= Change in Energy

24.99= 1/2mv squared

24.99= 1/2(15)v squared

3.332m/s=v

3.3m/s=v

This is unfortunately not the correct answer. If anyone can assist me in where i went wrong that would be great!

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# Homework Help: 2 boxes with energy attempt

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