Posted by **roxy** on Thursday, October 22, 2009 at 12:54pm.

An object has a gravitational potential energy of 24 joules when it rests on a shelf 3 m above the ground. What would be its gravitational potential energy when it is lowered to a shelf 1 m above the ground?

o A. 8 joules

o B. 12 joules

o C. 22 joules

o D. 72 joules

- physics -
**James**, Monday, June 4, 2012 at 10:37pm
PE = mgh

Therefore m = PE/(g x h)

m = 24/(9.8 x 3)

m = 0.82kg

Now the object is moved to 1m above the ground.

PE = mgh

PE = 0.82 x 9.8 x 1

PE = 8.036

Round off to 8 (A)

Alternatively, you could divide 24J by 3, as this is the change in height difference. But you may be marked down if proper work is not shown.

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