(a) Explanation Given data: Length of the escalator (displacement) ( d ) is 7.0 m. Distance from higher level to the lower level (height) ( h ) is 4 m. Formula used: Write the expression for work done by the force as follows. W = F d cos θ (1) Here, F is the applied force, d is the displacement, and θ is the angle between applied force and the direction of displacement. Write the expression for force as follows. F = m a (2) Here, m is the mass of the person, and a is the acceleration due to gravity, which is 9.8 m s 2 . From equation (2), substitute m a for F in equation (1). W = m a d cos θ (3) Modify the expression to find the work done by the up escalator on the person as follows. W up = m a d cos ( θ up ) (4) Here, θ up is the angle between the force exerted by the up escalator on the person and the direction of displacement. Consider length of the escalator and height of the level (from lower to higher) forms a right angle triangle with the floor. Then, write the expression for cosine of the angle between the force exerted by the escalator on the person and the direction of displacement as follows. cos ( θ up ) = h d Substitute 4.5 m for h , and 7.0 m for d . cos ( θ up ) = 4 (b) To determine To find: The work done by the down escalator on the person.

College Physics: A Strategic Approach (3rd Edition)

3rd Edition

ISBN: 9780321879721

Author: Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field

Publisher: PEARSON

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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 10, Problem 4P

(a)

To determine

To find: The work done by the up escalator on the person.

(b)

To determine

To find: The work done by the down escalator on the person.

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College Physics: A Strategic Approach (3rd Edition)

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The work done by the up escalator on the person.

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To find: The work done by the up escalator on the person.

To find: The work done by the down escalator on the person.

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Chapter 10 Solutions