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An escalator is used to move 5 people (each of mass 60 kg) per minute from the first floor to the second floor of a department store, which is 20 m above the first floor. Neglecting friction, calculate the minimum power (in kW) required by the escalator motor.

1. 0.1 kW
2. 0.3 kW
3. 1.0 kW
4. 0.5 kW

Correct answer: 0.1 kW

Solution

Power = (total energy transferred per unit time). Per minute: 5 people each 60 kg are raised 20 m. Energy = 5 * 60 * 10 * 20 = 60000 J. Time = 60 s. Power = 60000/60 = 1000 W = 1 kW.

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