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FIGURE Q10.12is the energy bar chart for a firefighter sliding down a fire pole from the second floor to the ground. Let the system consist of the firefighter, the pole, and the earth. What are the bar heights of Wext, Kf, and UGf?

Short Answer

Expert verified

Since Weat and Ufis zero, Kf must be two blocks high.

Step by step solution

01

Introduction

The following is the energy conservation equation:

Ki+Ugi+Wes=Kr+Ugr+ΔEth

HereKiis the initial kinetic energy, Ugiinitial potential energy, Kfis the final kinetic energy, Ug,final potential energy. ΔEwhis the thermal energy and Wedis the work done by the external force.

02

Explanation

There is no work done if the pole and the earth are included in the system. Weat.Also, at the lowest position, there is no gravitational potential energy, but there is some kinetic energy. The heights of the bars on the right side should add up to the same amount as the heights of the bars on the left side. Since Weatand Ufis zero, Kfmust be two blocks high. The corresponding energy bar chart is as follows,

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