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# Chapter 10 Problems - page 2 / 19

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10.A merry-go-round is stationary.  A dog is running on the ground just outside its circumference, moving with a constant angular speed of 0.750 rad/s. The dog does not change his pace when he sees what he has been looking for: a bone resting on the edge of the merry-go-round one-third of a revolution in front of him.  At the instant the dog sees the bone (t = 0), the merry-go-round begins to move in the direction the dog is running, with a constant angular acceleration of 0.015 0 rad/s2.  (a) At what time will the dog reach the bone?  (b) The confused dog keeps running and passes the bone.  How long after the merry-go-round starts to turn do the dog and the bone draw even with each other for the second time?

###### Section 10.3 Angular and Linear Quantities

11.Make an order-of-magnitude estimate of the number of revolutions through which a typical automobile tire turns in 1 yr.  State the quantities you measure or estimate and their values.

12.A racing car travels on a circular track of radius 250 m. If the car moves with a constant linear speed of 45.0 m/s, find (a) its angular speed and (b) the magnitude and direction of its acceleration.

13.A wheel 2.00 m in diameter lies in a vertical plane and rotates with a constant angular acceleration of 4.00 rad/s2. The wheel starts at rest at t = 0, and the radius vector of a certain point P on the rim makes an angle of 57.3 with the horizontal at this time. At t = 2.00 s, find (a) the angular speed of the wheel, (b) the tangential speed and the total acceleration of the point P, and (c) the angular position of the point P.

14.Figure P10.14 shows the drive train of a bicycle whose wheels are 67.3 cm in diameter and having pedal cranks that are

17.5 cm long.  The cyclist pedals at a steady angular rate of 76.0 rev/min. The chain engages with a front sprocket 15.2 cm in diameter and a rear sprocket 7.00 cm in diameter. (a) Calculate the speed of a link of the chain relative to the bicycle frame.  (b) Calculate the angular speed of the bicycle wheels.  (c) Calculate the speed of the bicycle relative to the road.  (d) What pieces of data, if any, are not necessary for the calculations?

Figure P10.14

15.A discus thrower accelerates a discus from rest to a speed of 25.0 m/s by whirling it through 1.25 rev. Assume the discus moves on the arc of a circle 1.00 m in radius. (a) Calculate the final angular speed of the discus. (b) Determine the magnitude of the angular acceleration of the discus, assuming it to be constant. (c) Calculate the time interval required for the discus to accelerate from rest to 25.0 m/s.

16.A car accelerates uniformly from rest and reaches a speed of 22.0 m/s in 9.00 s. If the diameter of a tire is 58.0 cm, find (a) the number of revolutions the tire makes during this motion, assuming that no

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