Question

A 20 m long chain of linear mass density 0.4 kg m–1 is hanging freely from a rigid support. The power required to lift the chain upto the point of support in 2 s is

Answer 1

first of all find centre of gravity of chain.
here centre of gravity lies at the centre of length of chain . e.g., C.O.G = h = 10m/2 = 5m

given, mass density = 0.4 kg/m

length of chain , l = 20m

so, mass of chain = l × mass density
= 20 × 0.4 = 8 kg

so, potential energy of chain = mgh
= 8 × 10 × 5 = 400J

power = energy/time,

so, power = 400/2 = 200W

hence, power required to lift the chain upto the point of support in 2 s is 200W