Question

A 2 kg mass object fell freely from the top of the high-rise building 100 m high. If the friction with air is negligible and g = 10 m / s squared, the effort made by the weight of the object so that the object up to a height of 50m from the ground is?

Answer 1

m = 2 kg
h1 = 100 m
h2 = 50 mg = 10 m/s²W = ?

W = ∆PE

PE = m g ∆h
PE = 2 • 10 (100 - 50)
PE = 1000 J

Answer 2

initally velocity of object = 0
so, at 100 m height body have only potential energy .
e.g P.E1= mgH = 2 × 10 × 100 = 2000j

after falling 50 m , body have some velocity and height ( 50m from ground )
hence, body have both potential and kinetic energy .
but we know,
effort made by weight is potential energy and effort made by motion of body is kinetic energy .

hence, we require only potential energy

e.g P.E2 = 2 × 10 × 50 = 1000 j

Hence, effort made by weight of the object so that it height 50 m from ground . = P.E2 - P.E2 = 2000j - 1000j = 1000j