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Unformatted text preview: 1998 Multiple Choice Questions 1. A solid metal ball and a hollow plastic ball of the same external radius are released from rest in a large vacuum chamber. When each has fallen 1m, they both have the same a. inertia b. speed c. momentum d. kinetic energy e. change in potential energy 2. A student weighing 700 N climbs at constant speed to the top of an 8 m vertical rope in 10 s. The average power expended by the student to overcome gravity is most nearly a. 1.1 W b. 87.5 W c. 560 W d. 875 W e. 5,600 W 3. A railroad car of mass m is moving at speed v when it collides with a second railroad car of mass M which is at rest. The two cars lock together instantaneously and move along the track. What is the speed of the cars immediately after the collision? a. v /2 b. mv / M c. Mv / m d. ( m + M ) v / m e. mv/( m+M) 4. An open cart on a level surface is rolling without frictional loss through a vertical downpour of rain, as shown above. As the cart rolls, an appreciable amount of rainwater accumulates in the cart. The speed of the cart will a. increase because of conservation of momentum b. increase because of conservation of mechanical energy c. decrease because of conservation of momentum d. decrease because of conservation of mechanical energy e. remain the same because the raindrops are falling perpendicular to the direction of the cart's motion 5. Units of power include which of the following? I. Watt II. Joule per second III. Kilowatt-hour a. I only b. III only c. I and II only d. II and III only e. I, II, and III 6. A 2 kg object moves in a circle of radius 4 m at a constant speed of 3 m/s. A net force of 4.5 N acts on the object. What is the angular momentum of the object with respect to an axis perpendicular to the circle and through its center? a. 9 N m/kg b. 12 m 2 /s c. 13.5 kg m 2 /s 2 d. 18 N m/kg e. 24 kg m 2 /s. 7. Three forces act on an object. If the object is in translational equilibrium, which of the following must be true? I. The vector sum of the three forces must equal zero. II. The magnitudes of the three forces must be equal. III. All three forces must be parallel. a. I only b. II only c. I and III only d. II and III only e. I, II, and III 8. The graph above represents the potential energy U as a function of displacement x for an object on the end of a spring oscillating in simple harmonic motion with amplitude x . Which of the following graphs represents the kinetic energy K of the object as a function of displacement x ? 9. A child pushes horizontally on a box of mass m which moves with constant speed v across a horizontal floor. The coefficient of friction between the box and the floor is . At what rate does the child do work on the box?...
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