Lesson 7B: Rotational Motion, Rotational Dynamics, and Moment Of Inertia

Write your solutions to the following problems and submit them before 6 am on Monday, March 3rd.

Submit to the SUBMIT folder on Priscilla or as an attachment to an e-mail message to rfuller@unlinfo.unl.edu or using this Web form.

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  1. A phonograph turntable is turning at 3.49 rad/s (33 1/3 rev/min) and has a radius of 0.150 m. A friction brake brings it to rest with uniform acceleration in 15.0 s.

    1. What is the angular acceleration of the turntable?

    2. How many revolutions does it complete before stopping?

  2. You live on a disk-shaped asteroid of radius 200 m that is rotating as shown in the diagram.

    1. If the angular velocity of the asteroid is initially 0.02 rad/s and it completes 15 revolutions as its angular velocity decreases uniformly to 0.01 rad/s, what is the angular acceleration?

    2. How much time is required for the asteroid to complete the 15 revolutions as described in part a?

  3. A truck traveling 20 m/s has tires 1 m in diameter. Assume that no slippage occurs between the tires and pavement.

    1. What is the angular speed of a tire about its axle?

    2. If the tires complete 20 revolutions as the truck brakes uniformly to a halt from this speed, what is the angular acceleration of the tires? What is the average linear tangential acceleration of a point on the tread?

    3. From the point where the brakes are applied, how far does the truck travel before stopping?

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