Exam 3 Phys 111 Fall 2002 Version A Section______
NAME______SCORE ______
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The exam is closed book and closed notes. Half-page equation sheet is allowed only.
Make sure you put your name on the SCANTRON form.
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Part I (20 points) Put the answers to these 10 questions on your SCANTRON sheet. Your answer should be closest to the given answers. ______
1. Block A and block B are moving toward each other. Block A has a mass of 2 kg and a velocity of 50 m/s while block B has a mass of 4 kg and a velocity of 20 m/s. They collide and stick together. The common final speed is:
A. 3.3 m/s
B. 20.0 m/s
C. 30.0 m/s
D. 40. 5 m/s
E. 50 m/s
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2. A 3-g bullet is fired horizontally into a 10-kg block of wood suspended by a rope form the ceiling. The block swings in an arc, rising 3 mm above its lowest position. The velocity of the bullet was:
A. 2.0x103 m/s
B. 1.2x103 m/s
C. 0.8x103 m/s
D. 240 m/s
E. 8 m/s
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3. Blocks A and B are moving toward each other along the x axis. A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4 kg and a velocity of -25 m/s. They suffer an elastic collision and move off along the x axis. The kinetic energy transferred from A to B during the collision is
A. 0
B. 2500 J
C. 5000 J
D. 7500 J
E. 9000 J
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4. A wheel of diameter 3 cm has a 4-m cord wrapped around its periphery. Starting from rest, the wheel is given a constant angular acceleration of 2 rev/s2. The cord will unwind in
A. 12.5 s
B. 8.5 s
C. 6.5 s
D. 3.5 s
E. 1.5 s
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5. The rotational inertia of a solid uniform sphere about a diameter is (2/5) MR2, 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. MR2,
B. (1/5) MR2,
C. (3/5) MR2,
D. (4/5) MR2,
E. (7/5) MR2,
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Exam 3 Phys 111 Fall 2002 Version A
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6. A disk with a rotational inertia of 5 kgm2 and a radius of 0.25 m rotates on a fixed axis perpendicular to the disk and through its center. A force of 2 N is applied tangentially to the rim. As disk turns through half a revolution the work done by the force is
A. 1.6 J
B . 3.5 J
C. 6.3 J
D. 8.5 J
E. 9.8 J
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7. A 1.5-kg particle moves in the xy plane with velocity v = (4.2 i - 3.6 j) m/s. What is the angular momentum of the particle when its position vector is r = (1.5 i + 2.2 j ) m.
A. + 12 k kgm2/s2
B. - 22 k kgm2/s2
C. -36 k kgm2/s2
D. +42 k kgm2/s2
E. -55 k kgm2/s2
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8. An 8.0 kg block is attached to a cord that is wrapped around the rim of a pulley of rotational inertia I = 1.4 kgm2and radius of 20 cm and hangs vertically, as shown. When the block is released and the cord unwinds, the acceleration of the block is
A. 0.63 m/s2
B. 1.28 m/s2
C. 1.82 m/s2
D. 3.53 m/s2
E. 4.34 m/s2
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9. A playground merry-go-round has a radius of 2 m and a rotational inertia of 300 kg m2. When the merry-go-round is at rest, a 30-kg child runs at 5 m/s along a line tangent to the rim and jumps on it. The angular velocity of the merry-go-round is then:
A. 0. 25 rad/s
B. 0.71 rad/s
C. 2.52 rad/s
D. 4.90 rad/s
E. 6.25 rad/s
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10. In figure a 1.0 g bullet is fired into a 0.50 kg block that is mounted on the end of a 0.60 m uniform rod of mass 0.50 kg. The block–rod–bullet system then rotates about a fixed axis at
point A. Assume the block is small enough to treat as a particle on the end of the rod. If the speed of the bullet just before the impact is 200 m/s, what is the angular speed of the block–rod–bullet system about A just after the bullet's impact?
A. 0. 5 rad/s
B. 0.9 rad/s
C. 2.5 rad/s
D. 4.9 rad/s
E. 6.6 rad/s
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