What is the gravitational potential energy of a # 12 kg# object on a shelf # 5/8 m # high?

1 Answer
Apr 14, 2018

Answer:

#73.5J#

Explanation:

Take #g=9.81 ms^-2# for the purpose of this question.

#E_g=mgh#

Since the mass #m=12#, and "height" #h=5/8#:

#E_g=12xx9.81xx5/8#

#E_g=2943/40#
#E_g=73.5J# (3 sig fig).

Since this is energy, the unit is joules (J)

Derivation of the formula - a little bonus

We can think about this formula as the work done lifting an object.

#"Work done"=Fxxs#

When work is done lifting an object against its weight, the force work is done to is its weight.

#W=mg#

Say the object is lifted a distance #h"m"#. Then our formula for work becomes:

#"Work done"=mgh#

This is equal to the gain in gravitational energy. Therefore:

#E_g=mgh#