Given :
Mass of the object
M=40kg
Height upto which it is raised
h=5m
Potential energy
P.E=Mgh
P.E=40×10×5=2000J
Let its kinetic energy be Ek when it is half way down i.e.
h'=h/2
According to conservation of energy,
K.Ei+P.Ei=K.Ef+P.Ef
0+2000=Ek+Mgh/2
∴2000=Ek+40×10×5/2
⇒Ek=1000J