A75-kg refrigerator is located on the 70th floor of a skyscraper (300 meters above the ground) what is the potential energy of the refrigerator?

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 :)

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.

I'm not sure what your asking buddy.. but i know that you can weld two peices of steel by pure force and pressure.

Velocity is the speed of an object in a certain direction so you'd need to know speed and direction