Question

a. A crane at a construction site lifts a concrete block with a mass of m = 277 kg from the ground to the top of a building with a height of h = 22.3 m. How much work did the motor of the crane do? (Assume zero energy loss in the lifting mechanism due to friction.)

b. If the duration of the lift was 2.85 minutes, then what was the average power performed by the crane?

Answer 1

a. The work motor of the crane did is 60.6 kJ.

b. The average power performed by the crane is 21.263kW.

What is work done?

Work done is equal to product of force applied and distance moved.

Work = Force x Distance

Given is  a crane at a construction site lifts a concrete block with a mass of m = 277 kg from the ground to the top of a building with a height of h = 22.3 m.

a. Work done by motor is  W= F x d

The force is equal to the weight F = mg

So, W = 277 x 9.81 x 22.3

W = 60.6 kJ

Thus, the work done by the motor is  60.6 kJ.

b. The duration of the lift was 2.85 minutes

Power = Work done/ time

Plug the values, we ghave

P = 60.6 x1000 /2.85

P =21.263kW

Thus, the  average power performed by the crane is 21.263kW

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