Question

A 75-kg refrigerator is located on the 70th floor of a skyscraper (300 meters above the ground) What is the potential energy of the refrigerator?

Answer 1

Potential energy = (mass) x (gravity) x (height above the reference) .

-- Relative to the 70th floor, the refrigerator's PE is zero.

-- Relative to the 69th floor,

PE = (75 kg) (9.8 m/s²) (~ 4.29 m) = ~ 3,150 joules .

--Relative to the ground,

PE = (75 kg) x (9.8 m/s²) x (300 m) = 220,500 joules.

Answer 2

Formula for potential energy is V=mgh, where m is mass in KG, g is earth acceleration (10 m/s^2), and h its height in meters. We know mass, acceleration is constant and also known, we know height also. Lets substitute
V=75*10*300=225000[J]=225[kJ] - its the answer :)