# Physics question on energy - need help !

1. Sep 29, 2013

### nish123

1. The problem statement, all variables and given/known data
Hello All !

I have this question which I cant seem to get the correct ans to.. maybe Im missing something.. (Please refer to attachment)

2. Relevant equations

POtential energy = mass x g x h

3. The attempt at a solution

ok initial amt of energy = m x g x h

final energy state =( mgh/4 + mgh/4 )= mgh/ 2

so mgh - mgh/2 = mgh/2 (my ans)

apparently correct ans is mgh/4

help , pls ? thanks !

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2. Sep 29, 2013

### Staff: Mentor

Hi nish123, Welcome to Physics Forums.

When dealing with changes in potential energy, you want to consider the change in elevation of the center of mass.

3. Sep 29, 2013

### nish123

ahh, got it!... thanks a ton
gneill and
ResscuedByMary

point i was missing was "When dealing with changes in potential energy, you want to consider the change in elevation of the center of mass."

Thanks again !!

4. Sep 29, 2013

### nish123

thanks ResscuedByMary i now understand your explanation too...

"When dealing with changes in potential energy, you want to consider the change in elevation of the center of mass." was told by
gneill as above... thanks both !