Answer:
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
