# Ch08 - Chapter 8, Rotational Equilibrium and Rotational...

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Chapter 8, Rotational Equilibrium and Rotational Dynamics C HAPTER 8 3. If a net torque is applied to an object, that object will experience: a. a constant angular speed b. an angular acceleration c. a constant moment of inertia d. an increasing moment of inertia 4. According to Newton’s second law, the angular acceleration experienced by an object is directly proportional to: a. its moment of inertia b. the net applied torque c. the object’s size d. choices a and b above are both valid 6. A ventilation fan with a moment of inertia of 0.034 kg m 2 has a net torque of 0.11 N m applied to it. If it starts from rest, what angular momentum will it have 8.0 s later? a. 0.88 kg m 2 /s b. 0.97 kg m 2 /s c. 2.0 kg m 2 /s d. 3.25 kg m 2 /s 7. A ventilation fan with a moment of inertia of 0.034 kg m 2 has a net torque of 0.11 N m applied to it. If it starts from rest, what kinetic energy will it have 8.0 s later? a. 31 J b. 17 J c. 11 J d. 6.6 J 8. A disk has a moment of inertia of 3.0 × 10 4 kg m 2 and rotates with an angular speed of 3.5 rad/sec. What net torque must be applied to bring it to rest within 3 s? a. 4.5 × 10 3 N m b. 7.5 × 10 4 N m c. 3.5 × 10 4 N m d. 5.0 × 10 4 N m 89

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Chapter 8, Rotational Equilibrium and Rotational Dynamics 9. A figure skater with arms initially extended starts spinning on the ice at 3 rad/s. She then pulls her arms in close to her body. Which of the following results? a. a smaller rotational rate b. a greater rotational rate c. a greater angular momentum d. a smaller angular momentum 10. The total kinetic energy of a baseball thrown with a spinning motion is a function of: a. its linear speed but not rotational speed b. its rotational speed but not linear speed c. both linear and rotational speeds d. neither linear nor rotational speed 11. The Earth moves about the Sun in an elliptical orbit. As the Earth moves closer to the Sun, which of the following best describes the Earth-Sun system’s moment of inertia? a. decreases b. increases c. remains constant d. none of the above choices are valid 12. A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 × 10 2 kg m 2 and a radius of 0.10 m. If it rolls down the lane without slipping at a linear speed of 4.0 m/s, what is its angular speed? a. 0.80 rad/s b. 10 rad/s c. 0.050 rad/s d. 40 rad/s 13. A bowling ball has a mass of 7.0 kg, a moment of inertia of 2.8 × 10 2 kg m 2 and a radius of 0.10 m. If it rolls down the lane without slipping at a linear speed of 4.0 m/s, what is its total kinetic energy? a. 45 J b. 32 J c. 11 J d. 78 J 90
Chapter 8, Rotational Equilibrium and Rotational Dynamics 15. A baseball pitcher loosens up his pitching arm. He tosses a 0.15-kg ball using only the rotation of his forearm, 0.32 m in length, to accelerate the ball. What is the moment of inertia of the ball alone as it moves in a circular arc with a radius of 0.32 m?

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## This note was uploaded on 07/25/2008 for the course PHY 231C taught by Professor Pratt during the Spring '06 term at Michigan State University.

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Ch08 - Chapter 8, Rotational Equilibrium and Rotational...

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