MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Diagram 1 A) B - A. B) A - B. C) A + B. D) A B.

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1 Exam Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) In the diagram shown, the unknown vector is 1) Diagram 1 A) B - A. B) A - B. C) A + B. D) A B. 2) Ignoring air resistance, the horizontal component of a projectile's velocity A) continuously increases. B) remains constant. C) is zero. D) continuously decreases. 3) A ball is thrown with a velocity of 20 m/s at an angle of 60e above the horizontal. What is the horizontal component of its instantaneous velocity at the exact top of its trajectory? A) zero B) 20 m/s C) 17 m/s D) 10 m/s 4) Three vectors, expressed in Cartesian coordinates, are 2) 3) 4) x comp y comp S T U What is the angle of the resultant vector S + T + U measured from the positive x axis? A) 66e above B) 24e above C) 24e below D) 66e below 1

2 FIGURE 3-1 5) Two forces are acting on an object as shown in Fig What is the magnitude of the resultant force? A) 198 N B) 200 N C) 47.5 N D) 185 N 6) When you sit on a chair, the resultant force on you is A) depending on your weight. B) up. C) down. D) zero. 7) When the rocket engines on the starship NO-PAIN-NO-GAIN are suddenly turned off, while traveling in empty space, the starship will A) slowly slow down, and then stop. B) go faster and faster. C) stop immediately. D) move with constant speed. 8) You are standing in a moving bus, facing forward, and you suddenly fall forward. You can imply from this that the bus's A) speed remained the same, but it's turning to the right. B) velocity decreased. C) speed remained the same, but it's turning to the left. D) velocity increased. 9) A net force F accelerates a mass m with an acceleration a. If the same net force is applied to mass 2m, then the acceleration will be A) 2a. B) a/4. C) a/2. D) 4a. 10) A 20-N weight and a 5.0-N weight are dropped simultaneously from the same height. Ignore air resistance. Compare their accelerations. A) The 20 N weight accelerates faster because it has more inertia. B) The 5.0 N weight accelerates faster because it has a smaller mass. C) The 20 N weight accelerates faster because it is heavier. D) They both accelerate at the same rate because they have the same weight to mass ratio. 11) A block of mass M slides down a frictionless plane inclined at an angle q with the horizontal. The normal reaction force exerted by the plane on the block is A) zero, since the plane is frictionless. B) Mg. C) Mg sin q. D) Mg cos q. 5) 6) 7) 8) 9) 10) 11) 2

3 12) An object sits on a frictionless surface. A 16-N force is applied to the object, and it accelerates at 2.0 m/s2. What is the mass of the object? A) 32 kg B) 78 N C) 8.0 kg D) 4.0 kg 12) 13) An antitank weapon fires a 3.00-kg rocket which acquires a speed of 50.0 m/s after traveling 90.0 cm down a launching tube. Assuming the rocket was accelerated uniformly, what is the average force acted on it? 13) A) N B) N C) N D) N 14) If you push a 4.0-kg mass with the same force that you push a 10-kg mass from rest, A) the 4.0-kg mass accelerates 2.5 times faster than the 10-kg mass. B) the 10-kg mass accelerates 2.5 times faster than the 4.0-kg mass. C) both masses accelerate at the same rate. D) None of the above is true. 14) 15) What is the mass of an object that weighs 250 N on the surface of the Earth where the acceleration due to gravity is 9.80 m/s2? A) 2,450 kg B) 250 kg C) 25.5 kg D) 24.5 kg 15) 16) A stack of books rests on a level frictionless surface. A force F acts on the stack, and it accelerates at 3.0 m/s2. A 1.0 kg book is then added to the stack. The same force is applied, and now the stack accelerates at 2.0 m/s2. What was the mass of the original stack? A) 2.0 kg B) 1.0 kg C) 3.0 kg D) none of the above 16) 17) Two horizontal forces act on a 5.0-kg mass. One force has a magnitude of 8.0 N and is directed due north. The second force toward the east has a magnitude of 6.0 N. What is the acceleration of the mass? 17) A) 1.2 m/s2 due east B) 2.0 m/s2 at 53e N of E C) 2.0 m/s2 at 53 m E of N D) 1.6 m/s2 due north FIGURE ) In the Atwood machine shown in Fig. 4-1, if M = 0.60 kg and m = 0.40 kg, what is the magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley.) A) 2.0 m/s2 B) 0.98 m/s2 C) 5.3 m/s2 D) 3.9 m/s2 18) 3

4 19) A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37e above the horizontal. If the mass of the box and the books is 40.0 kg, what is the acceleration of the box? A) 1.9 m/s2 B) 2.0 m/s2 C) 3.3 m/s2 D) 1.5 m/s2 19) FIGURE ) A traffic light of weight 100 N is supported by two ropes as shown in Fig What are the tensions in the ropes? A) 66 N B) 83 N C) 63 N D) 50 N 20) FIGURE ) Two boxes of masses m and 2m are connected by a rope. (See Fig. 4-4.) If the forward force on the more massive box is F, what is the tension in the connecting rope? A) 3F B) F/3 C) F D) F/2 21) 4

5 ESSAY. Write your answer in the space provided or on a separate sheet of paper. FIGURE ) Two boxes are connected by a cord running over a pulley as shown in Fig Box I of mass 8.0 kg rest on the top of the table; the coefficient of kinetic friction between box I and the table is Box II has a mass of 15.0 kg. (a) Draw the free-body diagrams for the two boxes, identifying all of the forces acting on each of the masses. (b) Calculate the acceleration of the system. (c) Calculate the tension in the cord. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 23) A 10-kg box sitting on a horizontal surface is pulled by a 5.0-N force. A 3.0-N friction force retards the motion. What is the acceleration of the object? A) 0.30 m/s2 B) 0.20 m/s2 C) 5.0 m/s2 D) 0.50 m/s2 23) 24) During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the ice before it stops. What is the coefficient of kinetic friction between the puck and the ice? A) 0.12 B) 0.10 C) D) ) 25) When an object experiences uniform circular motion, the direction of the acceleration is A) is directed toward the center of the circular path. B) in the opposite direction of the velocity vector. C) in the same direction as the velocity vector. D) is directed away from the center of the circular path. 25) 26) What force is needed to make an object move in a circle? A) static friction B) weight C) centripetal force D) kinetic friction 26) 27) A car goes around a curve of radius r at a constant speed v. Then it goes around the same curve at half of the original speed. What is the centripetal force on the car as it goes around the curve for the second time, compared to the first time? A) twice as big B) four times as big C) one-fourth as big D) half as big 27) 5

6 28) The banking angle in a turn on the Olympic bobsled track is not constant, but increases upward from the horizontal. Coming around a turn, the bobsled team will intentionally "climb the wall," then go lower coming out of the turn. Why do they do this? A) to give the team better control, because they are able to see ahead of the turn B) to reduce the g-force on them C) to prevent the bobsled from turning over D) to take the turn at a faster speed 28) 29) An object moves with a constant speed of 30 m/s on a circular track of radius 150 m. What is the acceleration of the object? A) zero B) 6.0 m/s2 C) 0.17 m/s2 D) 5.0 m/s2 29) 30) The maximum speed around a level curve is 30.0 km/h. What is the maximum speed around a curve with twice the radius? (Assume all other factors remain unchanged.) A) 42.4 km/h B) 120 km/h C) 60.0 km/h D) 45.0 km/h 30) 31) How many revolutions per minute must a circular, rotating space station of radius 1000 m rotate to produce an artificial gravity of 9.80 m/s2? A) 0.85 rpm B) 0.65 rpm C) 0.75 rpm D) 0.95 rpm 31) 32) A stone, of mass m, is attached to a strong string and whirled in a vertical circle of radius r. At the exact top of the path the tension in the string is 3 times the stone's weight. The stone's speed at this point is given by A) (gr)1/2. B) 2gr. C) 2(gr)1/2. D) (2gr)1/2. 32) 33) A jet plane flying 600 m/s experiences an acceleration of 4g when pulling out of the dive. What is the radius of curvature of the loop in which the plane is flying? A) 1200 m B) 7100 m C) 640 m D) 9200 m 33) 34) A car goes around a flat curve of radius 50 m at a speed of 14 m/s. What must be the minimum coefficient of friction between the tires and the road for the car to make the turn? A) 0.80 B) 0.60 C) 0.20 D) ) 35) A horizontal curve on a bobsled run is banked at a 45e angle. When a bobsled rounds this curve at the curve's safe speed (no friction needed to stay on the run), what is its centripetal acceleration? A) 0.5 g B) 1.0 g C) 2.0 g D) none of the above 35) ESSAY. Write your answer in the space provided or on a separate sheet of paper. 36) A 175-kg ball on the end of a string is revolving uniformly in a horizontal circle of radius m. The ball makes 2.00 revolutions in a second. (a) Determine the speed of the ball. (b) Determine the ball's centripetal acceleration. (c) Determine the force a person must exert on opposite end of the string. 6

7 Answer Key Testname: PRACTICE TEST CHPT 3_4_5_NOV2012 1) A 2) B 3) D 4) D 5) D 6) D 7) D 8) B 9) C 10) D 11) D 12) C 13) D 14) A 15) C 16) A 17) B 18) A 19) B 20) B 21) B 22) (a) Box one is acted on by the force of gravity in a downward direction, the normal force due to the table top in an upward direction, the tension in the string toward the right, and the force of friction due to the table top toward the left. Box two is acted on by the force of gravity in a downward direction and the tension in the string in an upward direction. (b) 6.1 m/s2 (c) 56 N 23) B 24) B 25) A 26) C 27) C 28) D 29) B 30) A 31) D 32) C 33) D 34) D 35) B 36) (a) 6.28 m/s (b) 79.0 m/s2 (c) 13.8 N 7