Physics Benchmark 2 Study Guide - (with answers)

Transcription

1 Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. _d 1. A rope pulls horizontally on a 4-kg block. The floor exerts a 7N frictional force on the block. If the tension in the rope is 23N, what is the acceleration of the block? a. 3 m/s 2 c. 6 m/s 2 b. 2 m/s 2 d. 4 m/s 2 c 2. How much force is required to accelerate a 24 kg object at a rate of 12 m/s 2 for 14 seconds? a. 2 N c. 288 N b. 28 N d N c 3. A 90-kg trash can sits on the sidewalk. The approximate normal force acting on the can from the sidewalk is a. 90 N c. 900N b. 90 kg d. 900kg d 4. A 2 kg rubber ball is thrown with a velocity of 2 m/s and bounces back at 1.2 m/s. What is the magnitude of change in the ball s momentum? a. 1.6 kg m/s c kg m/s b. 2.4 kg m/s d. 6.4 kg m/s d 5. When two identical 10,000 kg freight cars, one with an initial velocity of 4 m/s to the right and the other at rest collide and couple, what will be their resultant velocity? a. 4 m/s c. 1 m/s b. 8 m/s d. 2 m/s c 6. A bowling ball collides with an identical bowling ball at rest. The total momentum of the balls a. is zero. c. remains constant. b. increases. d. decreases. a 7. If two objects collide, what must be true? Assume no outside forces act. a. momentum is always conserved. b. kinetic energy is always conserved. c. neither momentum nor kinetic energy is conserved. d. both momentum and kinetic energy are always conserved. a 8. Two objects move separately after colliding, and both the total momentum and total kinetic energy remain constant. Identify the type of collision. a. elastic c. inelastic b. nearly elastic d. perfectly inelastic Learn, Think, Live Page 1

2 a 9. A horse can trot at the rate of 15 ft/s. How long does it take him to trot 100 yards? a. 20 s c. 7.3 s b s d. 15 s d 10. A 7-kg mass is dropped 12 m to the ground. What is the change in gravitational potential energy for the mass? a J c. -28 J b J d. -840J c 11. Ball A has triple the mass and speed of ball B. What is the ratio of the kinetic energy of ball A to ball B. a. 6 c. 27 b. 3 d. 9 b 12. A blue billiard ball collides with a yellow billiard ball. Their combined momentum is conserved a. only if they are traveling in opposite directions and have the same mass. b. only if there are no external forces, since external forces change momentum. c. only if the collision is inelastic and the masses do not stick together. d. only if the ball with the larger mass has lower velocity and the ball with smaller mass has higher velocity d 13. During a two-body collision, which quantity is always conserved? a. Kinetic Energy c. Potential Energy b. force d. momentum a 14. Two sliding boxes collide and stick together. What is this kind of collision called? a. perfectly inelastic c. elastic b. perfectly elastic d. inelastic a_ 15. A crate, with mass equal to 100 kg is loaded into a truck by traveling up a high-speed conveyor belt at a constant 6 m/s. The same box is unloaded at the end of the trip by traveling down a conveyor belt at a constant 4½ m/s. If you take gravity into account, when is the momentum of the box greatest? a. when the box is loaded c. it is equal, since the mass remains the same b. when the box is unloaded d. at the top of the ramp b 16. A ball attached to a string is swung in a circular path at constant speed. The velocity vector of the ball is a. perpendicular to the plane of the motion. c. perpendicular to the circle b. perpendicular to the acceleration vector d. parallel to the string Learn, Think, Live Page 2

3 c 17. A girl riding on the edge of a merry-go-round undergoes centripetal acceleration. Which direction is the force acting on her? a. Tangent to the edge of the merry-go-round pointing in the direction of motion b. tangent to the radius of the merry-go-round pointing at the girl c. pointing from the girl to the center of the merry-go-round d. pointing outward from the center of the merry-go-round toward the girl a 18. Mr. Towne goes to Costco to buy soda. He loads 8 cases into the bed of his pick-up. On the way home, he makes a sharp right turn and all the cases slide to the left side of the truck. What caused this? a. inertia c. centrifugal force b. centripetal force d. centripetal acceleration c 19. The International Space Station is in orbit around the planet Earth. Astronauts in the station appear weightless. Why? a. Because no gravitational force is acting on them. b. Because the net forces acting on them are zero. c. Because the gravitational force acting on them is not counteracted by a normal force. d. Because the net gravitational force acting on the astronauts is so small it is negligible. a 20. The tendency of an object to resist acceleration is a. inertial mass c. gravitational resistance b. gravitational mass d. weight d 21. What is the technical term that refers to the tendency of a force to cause a rotation or spinning motion about an axis of rotation? a. lever arm c. centripetal acceleration b. centripetal d. torque a 22. In the days of Kepler, most people believed the was the center of the Universe. a. Earth c. The Milky Way Galaxy b. Sun d. A Black Hole d 23. A 100 gram tennis ball with an initial velocity of 65 m/s strikes a wall and bounces back with a velocity of 35 m/s. What is the magnitude of its change in momentum? a. 3 Kg X m/s c. 6.5 Kg X m/s b. 30 Kg X m/s d. 10 Kg X m/s b 24. If a very small force is applied to an object with a very large mass, which statement is definitely true? a. There will be very little change in the object s momentum. b. The longer the force is applied, the more the momentum will change. c. There will be a large change in momentum, since momentum is inversely proportional to force. d. The momentum will increase, but so slightly it cannot be measured. Learn, Think, Live Page 3

4 a 25. Force can be defined as a. The rate of change of momentum b. The rate of change of velocity c. The rate of change of displacement multiplied by mass. d. The rate of change of acceleration multiplied by mass. b 26. The impulse experienced by a body is equivalent to the body s change in a. force. c. kinetic energy. b. momentum d. velocity a 27. A low velocity billiard ball collides with another billiard ball at rest. The total momentum of the balls a. remains constant c. is zero b. decreases d. depends on the inertia of the balls b 28. If two objects collide, a. kinetic energy is always conserved. b. momentum is always conserved. c. both momentum and kinetic energy are always conserved. d. neither momentum nor kinetic energy is conserved. a 29. Object A strikes object B. After the collision, both objects are moving in the negative direction. The combined momentum before the collision is equal to the combined momentum after the collision. The total initial kinetic energy is equal to the total final kinetic energy. Identify the type of collision: a. elastic c. inelastic b. nearly elastic d. perfectly inelastic c 30. When is linear momentum conserved? a. When all forces are linear forces. b. When the magnitude of the linear forces is greater than the magnitude of nonlinear forces. c. When the net force on the system is zero. d. When the internal forces are greater than the external forces on the system. d 31. A boy is sitting in a wagon, which is rolling down a hill at 25 m/s. The combined mass of the wagon and child is 200 kg. The momentum of the boy and wagon is a. 8 kilogram m / s c kilogram m / s b. 25 kilogram m / s d kilogram m / s c 32. A boy coasts down a hill on a bicycle with frictionless wheels. Assuming no forces other than gravity are acting on him Which quantity remains constant? a. Potential Energy c. Total Mechanical Energy b. Kinetic Energy d. Momentum Learn, Think, Live Page 4

5 a 33. A 10 ton rail car moving at 4 m/s east strikes a 30 ton rail car, which is at rest. The cars latch and couple, what is their resultant velocity? a. 1 m/s c. 4 m/s b. 2 m/s d. 8 m/s a 34. Which of the following is a physical quantity that has both magnitude and direction? a. vector c. resultant b. scalar d. frame of reference b 35. Which of the following is the tendency of an object to maintain its state of motion? a. acceleration c. force b. inertia d. velocity c 36. If a nonzero net force is acting on an object, then the object is definitely a. at rest. c. being accelerated. b. moving with a constant velocity. d. losing mass. b 37. Gravitational potential energy is always measured in relation to a. total potential energy. c. kinetic energy. b. a zero level. d. mechanical energy. b 38. Which of the following is the rate at which work is done? a. kinetic energy c. mechanical energy b. power d. potential energy d 39. A BASE jumper jumps off a 120 m tower. If no air resistance is present, there will be a decrease in her a. Kinetic Energy c. Total Energy b. Momentum d. Gravitational Potential Energy a 40. In question 40 above, there will be an increase in her a. Kinetic Energy b. Gravitational Potential Energy c. Elastic Potential Energy d. Mass Learn, Think, Live Page 5

6 Constructed response: Physics Benchmark 2 Study Guide - (with answers) 41. A hiker travels south along a straight path for 1.5 h with an average speed of 0.75 km/h and then travels north for 2.5 h with an average speed of 0.90 km/h. What is the hiker s displacement for the total trip? 42. Someone throws a rubber ball vertically upward from the roof of a building 8.00 m in height. The ball rises, then falls. It just misses the edge of the roof, and strikes the ground. If the ball is in the air for 3.00 s, what was its initial velocity? (Disregard air resistance. a = g = 9.81 m/s.) 43. A warehouse worker pulls on the handles of a 96.0 kg cart with a net force of 128 N an angle of 55.0 above the horizontal. Attached to the cart is a smaller cart having a mass of 72.0 kg. What is the magnitude of the horizontal acceleration of the less massive cart? 44. A rubber ball with a mass of 0.30 kg is dropped onto a steel plate. The ball s speed just before impact is 4.5 m/s and just after impact is 4.2 m/s. What is the change in the ball s momentum? 45. A diver with a mass of 80.0 kg jumps from a dock into a kg boat at rest on the west side of the dock. If the velocity of the diver in the air is 4.10 m/s to the west, what is the final velocity of the diver after landing in the boat? 46. A clay ball with a mass of 0.35 kg strikes another 0.35 kg clay ball at rest, and the two balls stick together. The final velocity of the balls is 2.1 m/s north. What was the first ball s initial velocity? Learn, Think, Live Page 6