Question 1 Before beginning this Reading Quiz, you should have read Chapter 10:3

Question

Question 1 Before beginning this Reading Quiz, you should have read Chapter 10:3 ( -pages 309-314) As shown in the figure, an ab roller is an exercise device for training the abdominal muscles; it is simply a wheel (W) with a pair of handles at its axle. You are observing a trainer (T) who is using the ab roller on a level floor (F). The device is always rolling without slipping and is sometimes speeding up but at other times is slowing down. When the ab roller is slowing down, what is the direction of the frictional force on the ab roller by the floor? In particular, consider the case in which the ab roller is near the end of its lefward motion, as might possibly be the case in the right-hand figure below. At such an instant the ab roller is still moving leftward but is slowing down. To answer such a question, you would need to make a good free-body diagram and apply the Second Law for translation and for rotation of the system of particles that is the ab roller. The questions below will ask you to consider two possible free-body diagrams for this situation

Explanation / Answer

partA] third option is correct.

Since it is slowing down, its angular speed should also decrease which means angular acceleration should be clockwise, but in diagram it is CCW.

partB] first option is correct.

Since it is slowing down, the acceleration should be towards right. So net horizontal force should be towards right.

partC] first option is correct.

Here friction will provide clockwise angular acceleration for slowing down angular speed and since it is weaker than horizontal force by trainer, it will acceleration will be towards right.

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