Q. Water is drawn from a well in a 5 kg drum of capacity 55 L by two ropes connected to the top of the drum. The linear mass density of each rope is $0.5\ kgm^{- 1}$. The work done in lifting water to the ground from the surface of water in the well 20 m below is $\lbrack g = 10ms^{- 2}\rbrack$
A) $1.4 \times 10^{4}\ J$
B) $1.5 \times 10^{4}\ J$
C) $9.8 \times 10^{\ } \times 6\ J$
D) $18\ J$
Explanation
(a) Work done in lifting water and drum
$= 60 \times 10 \times 20\ J = 12000\ J$
Total mass of ropes $= 40 \times 0.5$ kg= 20 kg
Work done in the case of ropes
$= 20 \times 10 \times 10 = 2000\ J$
Total work done = 14000 J
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.