Question

An object of mass 1 kg is falling from the height h = 10 m. Calculate potential energy of the object when it is at h = 4m

Answer 1

Answer:

according to conservation of mechanical energy

PEi +KEi = PEf +KEf

mgh +0 = PE f + KE f

mgh = 1× 10×10 = 100 J

v at 4m = √2gh

= √2×10×40 = √800 = 20√2

therefore KEf = 1/2 ×m ×v^2

= 1/2 ×1× 800= 400

now PE f = 100-400 = -300 J