What is the potential energy of a 3 kg rock sitting at the top of a 21 meter high cliff?

618.03 J

Explanation:

Potential energy can be calculate using the following formula.

PE=m*g*h

where m is the mass, g is the acceleration due to gravity and h is the height.

In this situation, we have a 3 kilogram rock on a 21 meter high cliff. Therefore, the mass is 3 kg and the height is 21 m.

On Earth, the acceleration due to gravity is 9.81 m/s^2.

m=3 kg

h=21 m

g=9.81 m/s^2

Substitute these values into the formula.

PE=3*9.81*21

Multiply all the numbers together

PE=63*9.81

PE=618.03

The potential energy is 618.03 kg m^2/s^2, or 618.03 Joules

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