Work and Power in Cycling When you ride a bicycle at constant speed, almost all of the energy you expend goes into the work you do against the drag force of the air. In this problem, assume that all of the energy expended goes into working against drag. As we saw in Section 5.7, the drag force on an object is approximately proportional to the square of its speed with respect to the air. For this problem, assume that F α v 2 exactly and that the air is motionless with respect to the ground unless noted otherwise. Suppose a cyclist and her bicycle have a combined mass of 60 kg and she is cycling along at a speed of 5 m/s. 89. How much power does she expend when cycling at that speed? A. 100 w B. 200 W C. 400 W D. 1000 W
Work and Power in Cycling When you ride a bicycle at constant speed, almost all of the energy you expend goes into the work you do against the drag force of the air. In this problem, assume that all of the energy expended goes into working against drag. As we saw in Section 5.7, the drag force on an object is approximately proportional to the square of its speed with respect to the air. For this problem, assume that F α v 2 exactly and that the air is motionless with respect to the ground unless noted otherwise. Suppose a cyclist and her bicycle have a combined mass of 60 kg and she is cycling along at a speed of 5 m/s. 89. How much power does she expend when cycling at that speed? A. 100 w B. 200 W C. 400 W D. 1000 W
When you ride a bicycle at constant speed, almost all of the energy you expend goes into the work you do against the drag force of the air. In this problem, assume that all of the energy expended goes into working against drag. As we saw in Section 5.7, the drag force on an object is approximately proportional to the square of its speed with respect to the air. For this problem, assume that F α v2 exactly and that the air is motionless with respect to the ground unless noted otherwise. Suppose a cyclist and her bicycle have a combined mass of 60 kg and she is cycling along at a speed of 5 m/s.
89. How much power does she expend when cycling at that speed?
While cruising down University Boulevard you are stopped by a cop who states that you ran a red traffic light. Because you don't
want to pay the stiff fine, you are attempting a physics defense. You claim that due to the relativistic Doppler effect, the red color of
the light λ=616 nm appeared green '=531 nm to you. The cop makes a quick calculation of his own and rejects your defense.
How fast, in terms of your speed u divided by the speed of light in vacuum c, would you have to drive to justify your claim? Note
that the speed u is taken to be a positive quantity.
U 4.0
C
220 V is supplied to 800 primary turns of an autotransformer. What will the outputvoltage be across 200 secondary turns?
2. A filament transformer has a turns ratio of 1:20. What current must be supplied to theprimary windings if 5 A is required by the filament?
3. The filament transformer in the previous question is supplied with 150 V to theprimary side. What is the secondary voltage?
4. 440 V is supplied to 1000 primary turns of an autotransformer. If the desired outputvoltage is 100 V how many secondary turns must be tapped?
Chapter 10 Solutions
Student Workbook for College Physics: A Strategic Approach Volume 1 (Chs. 1-16)
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8.01x - Lect 11 - Work, Kinetic & Potential Energy, Gravitation, Conservative Forces; Author: Lectures by Walter Lewin. They will make you ♥ Physics.;https://www.youtube.com/watch?v=9gUdDM6LZGo;License: Standard YouTube License, CC-BY