Explanation 1) Concept: First, we identify all the forces involved in this process, and we find their corresponding work done. Then, we can find the total work done W . Finally, by using these values, we can find the average power p required of the force the motor exerts on the cab via the cable. 2) Formula: i) Work done by the gravity is, W = - m g d ii) The total work done is, W = W e + W c + W m 3) Given: i) Mass of the cab of freight elevator is, m e = 1200 K g ii) Mass of the counter weight of the elevator is, m c = 950 k g iii) Distance required to travel by the elevator is, d = 54 m . iv) Time interval required to travel a distance d by the elevator is, ∆ t = 3 m = 180 s . 4) Calculations: Here, the loaded elevator is moving upwards with a constant speed. Therefore, three forces are involved: a. Gravitational force exerted on the elevator and the corresponding work done is W e . b. Gravitational force exerted on the counter weight and the corresponding work done is W c . c. Force by the motor via cable and the corresponding work done is W m Therefore, the total work done is given as W = W e + W c + W m Since, the loaded elevator is moving upwards with a constant speed, the kinetic energy must be constant, and hence, the work done due to kinetic energy is zero. W = ∆ K = 0 Now, work done by gravity on the elevator is W e = - m e g d W e = - 1200 × 9

11th Edition

ISBN: 9781119459132

Author: Halliday

Publisher: WILEY

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Instantaneous Power

Power is defined in physics as the amount of energy transmitted or transformed per unit time. The watt is the unit of electricity in the International System of Units, equivalent to one joule per second.

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Chapter 7, Problem 49P

To determine

To find

The average power required of the force the motor exerts on the cab via the cable.

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Chapter 7 Solutions

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To find The average power required of the force the motor exerts on the cab via the cable.

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To find The average power required of the force the motor exerts on the cab via the cable.

Chapter 7 Solutions

To find

The average power required of the force the motor exerts on the cab via the cable.