posted by HELP ASAP on .
(i) A 20m chain with a mass-density of 3kg/m (coiled on the ground). How
much work is performed lifting the chain so that it is fully extended (and
one end touches the ground)?
(ii) How much work is performed to lift 1/4 of the chain?
This sounds like a physics problem:
Work done = increase in potential energy (PE)
PE at ground = 0
After lifting, the centre of gravity of the chain is at h=10 m above ground, so
=(3 kg/m * 20m)*9.8 m/s²*10m
= 5880 joules
ρ = length density = 3 kg/m
x=distance of top of chain from ground in metres
length of chain off ground = x
mass of chain off ground = ρx
weight of chain off ground = ρxg
lifting the chain through a distnce dx does work of
Total work done through a length of 0 to L metres
Work done = 14.7(20²)=5880 joules