hmwk-4-Fall-2006 - PHY 317K October 12, 2006 HOMEWORK # 4...

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PHY 317K October 12, 2006 HOMEWORK # 4 DUE on October 30, 2006 by 8:00pm Instructions: Use a SCANTRON ANSWER SHEET to mark answers. Provide your NAME (last, first), UT EID, and UNIQUE NUMBER of the course. Sign and date it. The answer sheets must be placed in the 317K box (by bulletin board outside PAI 2.48) by 8:00pm on Monday, October 30, 2006. Late homework will not be graded. Answer the following 56 questions: 1. A radian is about: A) 25 ° B) 37 ° C) 45 ° D) 57 ° E) 90 ° 2. One revolution per minute is about: A) 0.0524 rad/s B) 0.105 rad/s C) 0.95 rad/s D) 1.57 rad/s E) 6.28 rad/s 3. If a wheel turning at a constant rate completes 100 revolutions in 10 s its angular speed is: A) 0.31 rad/s B) 0.63 rad/s C) 10 rad/s D) 31 rad/s E) 63 rad/s 4. A flywheel, is initially rotating at 20 rad/s and has a constant angular acceleration. After 9.0 s it has rotated through 450 rad. Its angular acceleration is: A) 3.3 rad/s 2 B) 4.4 rad/s 2 C) 5.6 rad/s 2 D) 6.7 rad/s 2 E) 11 rad/s 2 Page 1
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5. A flywheel rotating at 12 rev/s is brought to rest in 6 s. The magnitude of the average angular acceleration in rad/s 2 of the wheel during this process is: A) 1/ π B) 2 C) 4 D) 4 π E) 72 6. A wheel initially has an angular velocity of 36 rad/s but after 6.0s its angular velocity is 24 rad/s. If its angular acceleration is constant the value is: A) 2.0 rad/s 2 B) –2.0 rad/s 2 C) 3.0 rad/s 2 D) –3.0 rad/s 2 E) 6.0 rad/s 2 7. A wheel starts from rest and has an angular acceleration that is given by α ( t ) = (6 rad/s 4 )t 2. The angle through which it turns in time t is given by: A) [(1/8) t 4 ] rad B) [(1/4) t 4 ] rad C) [(1/2) t 4 ] rad D) ( t 4 ) rad E) 12 rad 8. The angular velocity vector of a spinning body points out of the page. If the angular acceleration vector points into the page then: A) the body's rotation is slowing down B) the body's rotation is speeding up C) the body is starting to turn in the opposite direction D) the axis of rotation is changing orientation E) none of the above 9. For a wheel spinning with constant angular acceleration on an axis through its center, the ratio of the speed of a point on the outer rim to the speed of a point halfway between the center and the rim is: A) 1 B) 2 C) 1/2 D) 4 E) 1/4 Page 2
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10. Four identical particles, each with mass m , are arranged in the x , y plane as shown. They are connected by light sticks to form a rigid body. If m = 2.0 kg and a = 1.0 m, the rotational inertia of this array about the y -axis is: A) 4.0 kg m 2 B) 12 kg m 2 C) 9.6 kg m 2 D) 4.8 kg m 2 E) none of these 11. A and B are two solid cylinders made of aluminum. Their dimensions are shown. The ratio of the rotational inertia of B to that of A about the common axis X X' is: A) 2 B) 4 C) 8 D) 16 E) 32 12. The rotational inertia of a solid uniform sphere about a diameter is (2/5) MR 2 , where M is its mass and R is its radius. If the sphere is pivoted about an axis that is tangent to its surface, its rotational inertia is: A) MR 2 B) (2/5) MR 2 C) (3/5) MR 2 D) (5/2) MR 2 E) (7/5) MR 2 Page 3
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13. A rod is pivoted about its center. A 5-N force is applied 4 m from the pivot and another 5-N force is applied 2 m from the pivot, as shown. The magnitude of the total torque about
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This note was uploaded on 04/30/2008 for the course PHY 317k taught by Professor Kopp during the Fall '07 term at University of Texas at Austin.

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hmwk-4-Fall-2006 - PHY 317K October 12, 2006 HOMEWORK # 4...

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