Starting from rest, a 12-cm-diameter compact disk takes 3.5 s to reach its operating angular velocity of 1600 rpm. Assume that the angular acceleration is constant. The disk's moment of inertia is 2.5 x 10- kg m². Part A How much torque is applied to the disk? Express your answer to two significant figures and include the appropriate unit ? Value Units Submit Reguest Answer Part B How many revolutions does it make before reaching full speed? Express your answer using two significant figures. ΑΣή

Starting from rest, a 12-cm-diameter compact disk takes 3.5 s to reach its operating angular velocity of 1600 rpm. Assume that the angular acceleration is constant. The disk's moment of inertia is 2.5 x 10- kg m². Part A How much torque is applied to the disk? Express your answer to two significant figures and include the appropriate unit ? Value Units Submit Reguest Answer Part B How many revolutions does it make before reaching full speed? Express your answer using two significant figures. ΑΣή

Glencoe Physics: Principles and Problems, Student Edition

1st Edition

ISBN:9780078807213

Author:Paul W. Zitzewitz

Publisher:Paul W. Zitzewitz

Chapter8: Rotational Motion

Section: Chapter Questions

Problem 93A

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A baseball catcher extends his arm straight up to catch a fast ball with a speed of 40 m/s. The baseball is 0.145 kg and the catcher’s arm length is 0.5 m and mass 4.0 kg. (a) What is the angular velocity of the arm immediately after catching the ball as measured from the arm socket? (b) What is the torque applied if the catcher stops the rotation of his arm 0.3 s after catching the ball?
A wheel is rotating about a fixed axis with constant angular acceleration 3 rad/s2. At different moments, its angular speed is 2 rad/s, 0. and +2 rad/s. For a point on the rim of the wheel, consider at these moments the magnitude of the tangential component of acceleration and the magnitude of the radial component of acceleration. Rank the following five items from largest to smallest: (a) |at| when = 2 rad/s, (b)|ar| when = 2 rad/s, (c)|ar| when = 0, (d) |at| when = 2 rad/s, and (e) |ar| when = 2 rad/s. If two items are equal, show them as equal in your ranking. If a quantity is equal to zero, show that fact in your ranking.
There an analogy between rotational and physical quantities. What rotational quantities are analogous to distance and velocity?
A bicycle tire is spinning clockwise at 2.50 rad/s. During a time period t = 1.25 s, the tire is slopped and spun in the opposite (counterclockwise) direction, also at 2.50 rad/s. (Calculate (a) the change in the tires angular velocity and (b) the tire's average angular acceleration av.
Suppose you start an antique car by exerting a force of 300 N on its crank for 0.250 s. What angular momentum is given to the engine if the handle of the crank is 0.300 m from the pivot and the force is exerted to create maximum torque the entire time?
Olympic ice skaters are able to spin at about 5 rev/s. (a) What is their angular velocity in radians per second? (b) What is the centripetal acceleration of the skater's nose if it is 0.120 m from the axis of rotation? (c) An exceptional skater named Dick Button was able to spin much faster in the 1950s than anyone since—at about 9 rev/s. What was the centripetal acceleration of the tip of his nose, assuming it is at 0.120 m radius? (d) Comment on the magnitudes of the accelerations found. It is reputed that Button ruptured small blood vessels during his spins.
A grindstone increases in angular speed uniformly from 4.00 rad/s to 12.0 rad/s in 4.00 s. (a) Calculate the grindstones angular acceleration. (b) Through what angle does it turn during that time? (See Section 7.2.)
(a) What is the angular speed of the second hand of a clock? (b) What is the direction of as you view a clock hanging on a vertical wall? (c) What is the magnitude of the angular acceleration vector of the second hand?
Check Your Understanding The fan blades on a jet engine have a moment of inertia 30.0kgm2 . In 10s, they rotate counterclockwise from rest up to a rotation rate of 20 rev/s. (a) What torque must be applied to the blades to achieve this angular acceleration? (b) What is the torque required to bring the fan blades rotating at 20 rev/s to a rest in 20s?
A student rides his bicycle at a constant speed of 3.00 m/s along a straight, level road. If the bikes tires each have a radius of 0.350 m, (a) what is the tires angular speed? (See Section 7.3.) (b) What is the net torque on each tire? (See Section 8.5.)
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