A lift in a building can carry a maximum of 10 persons, with the average mass of each person being 68 Kg. The mass of the lift itself is 920 Kg and it moves with a constant speed of 3 m/s. The frictional force opposing the motion is 6000 N. If the lift is moving up with its full capacity, the power delivered by the motor to the lift `(g = 10 m//s^2)` must be at least:

Options

A. 62360 W
B. 56300 W
C. 48000 W
D. 66000 W

Answer

D

Explanation

Net force on motor will be
`F_m = [920 +68(10)]g + 6000 = 22000N`
So, required power for motor `P_m = vecF_(m) .vecv`
` = 22000 xx 3`
= 66000 Watt