Answer:
5.5 kg
Step-by-step explanation:
The gravitational potential energy of an object is given by

where
m is its mass
g is the acceleration of gravity
h is the height of the object above the ground
For the rock in the problem, we know:
h = 12 m is the height above the ground
U = 650 J
g = 9.8 m/s^2
Therefore, we can solve the equation for m, the mass of the rock:
