# A major department store has just installed three new escalators. Each one is designed to carry 120 people, each of average mass 70kg. per min to a floor 10.0m higher. The engine which drives these escalators is 65% energy efficient. What?

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What power must the engine develop?????

What power must the engine develop?????

##### 1 Answer

#### Explanation:

From the definition of average power

Meaning that the energy input to the escalator in one minute (

The effective work the escalator does in a one-minute interval is equal to the passengers' gain in gravitational potential energy in that amount of time. Taking the gravitational field strength

The escalator has an efficiency of

Note that