PHYSICS 6A PRACTICE QUIZ 7 THE FOLLOWING MULTIPLE CHOICE QUESTIONS ARE NOT TO BE TURNED IN FOR GRADING, THEY ARE INTENDED AS A SELF EVALUATION QUIZ AND PRACTICE FOR THE FINAL EXAM MULTIPLE CHOICE. Choose the ONE alternative that BEST completes the statement or answers the question. 1) A railroad car of mass m and speed v collides and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system A) is the same as before. B) is half as much as before. C) is one third as much as before. D) is one fourth as much as before. E) is one quarter as much as before. 2) A 50.0-kg person stands on a 200-kg raft, which is at rest. She starts to walk on the raft with a speed of 3.00 m/s with respect to the raft. What is the speed of the person relative to the water? A) 2.40 m/s B) 0.225 m/s C) 0.500 m/s D) 0.750 m/s E) 1.20 m/s 3) A 550-g mass traveling at 8.0 m/s undergoes a head-on elastic collision with a 250-g mass traveling toward it also at 8.0 m/s. What is the speed of the 250-g mass after the collision? A) 15 m/s B) 8.0 m/s C) 4.0 m/s D) 14 m/s E) 0 m/s 4) A pulley has an initial angular speed of 12.5 rad/s and a constant angular acceleration of 3.41 rad/s2. Through what angle does the pulley turn in 5.26 s? A) 113 rad B) 22.6 rad C) 42.6 rad D) 19.3 rad E) 160 rad 5) Suppose a solid sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The linear velocity of the sphere at the bottom of the incline depends on A) the mass of the sphere. B) the radius of the sphere. C) both the mass and the radius of the sphere. D) neither the mass nor the radius of the sphere.

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6) A pencil, 15.7 cm long, is released from a vertical position with the eraser end resting on a table. The eraser does not slip. Treat the pencil like a uniform rod. What is the angular speed of the pencil just before it hits the table? A) 13.7 rad/s B) 7.23 rad/s C) 3.70 rad/s D) 24.5 rad/s E) 16.8 rad/s

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