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Question

An elevator in a building can carry a maximum of 10 persons, with the average mass of each person being 68 kg. The mass of the elevator itself is 920 kg and it moves with a constant speed 3 m/s. The frictional force opposing the motion is 6000 N. If the elevator is moving up with its full capacity, the power delivered by the motor to the elevator (g=10m/s2) must be at least

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

The correct option is D 66000 W
Step1: Draw a free body diagram of the given problem.

Step2: Find the tension in the cable of the elevator.

The elevator moving with constant speed hence

T=10mg+Mg+f

T=6800+9200+6000

T=22000 N

Step3: Find the power supplied by the motor.

Formula used: P=F.v

The power delivered by the motor to the elevator
Power =T.v

=22000×3

=66000 W

Final Answer: (c)

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