Potential Energy = Mass * Gravitational Constant * Height
What We Don't Know: Potential Energy
What We Know:
Mass
Gravitational Constant (9.8 m/s)
Height
Ep = mgh
Ep = 4 * 9.8 * 2
Ep = 78.4 Joules
The Potential Energy of the Rock is 78.4 Joules, based on the given information! Hope this helps you!