F13--HPhys--Q5 Practice

Name: Class: Date: ID: A F13--HPhys--Q5 Practice Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A vector is a quantity that has a. time and direction. b. magnitude and time. c. magnitude and direction. 2. The law of inertia applies to a. objects at rest. b. moving objects. c. both moving and nonmoving objects. 3. One possible unit of speed is a. miles per hour. b. light years per century. c. kilometers per hour. d. all of the above. e. none of the above. 4. How much does a 3.0-kg bag of bolts weigh? a. 22.8 N b. 7.2 N c. 58.8 N d. 29.4 N e. 14.4 N 5. Suppose two people, one having three times the mass of the other, pull on opposite sides of a 20-meter rope while on frictionless ice. After a brief time, they meet. The more massive person slides a distance of a. 5 m. b. 6 m. c. 4 m. d. 7 m. 6. A sportscar has a mass of 1500 kg and accelerates at 5 meters per second squared. What is the magnitude of the force acting on the sportscar? a. 2250 N. b. 1500 N. c. 7500 N. d. 300 N. e. none of the above 7. In order to find the components of a vector, you should a. measure the sides of the rectangle. b. draw a rectangle so that the vector is the diagonal. c. draw the vector with correct magnitude and orientation. d. all of the above 8. What is the resultant of a 3-unit vector and 4-unit vector at right angles to each other? a. 5 units. b. 1 unit. c. 7 units. d. none of the above 9. Friction a. comes from microscopic bumps that act as obstructions to the object's motion. b. acts in a direction that opposes the motion of an object. c. is the name given to the force acting between surfaces sliding past one another. d. all of the above e. none of the above 10. Suppose a car is moving in a straight line and steadily increases its speed. It moves from 35 km/h to 40 km/h the first second and from 40 km/h to 45 km/h the next second. What is the car's acceleration? a. 10 km/h s b. 35 km/h s c. 5 km/h s d. 40 km/h s e. 45 km/h s 11. In the absence of air resistance, objects fall at constant a. distances each successive second. b. acceleration. c. velocity. d. speed. e. all of the above 12. A cannonball is launched from the ground at an angle of 30 degrees above the horizontal and a speed of 30 m/s. Ideally (no air resistance) the ball will land on the ground with a speed of a. There is not enough information to say. b. 20 m/s. c. 30 m/s. d. 0 m/s. e. 40 m/s. 13. If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the tube first? a. The feather b. Neither-they will both reach the bottom at the same time. c. The coin 14. Friction is a force that always acts a. perpendicular to an object's motion. b. in the same direction as an object's motion. c. opposite to an object's motion. 15. The horizontal component of a projectile's velocity is independent of a. the range of the projectile. b. the vertical component of its velocity. c. time. 1

Name: ID: A 16. A player hits a ball with a bat. The action force is the impact of the bat against the ball. What is the reaction to this force? a. Air resistance on the ball b. The grip of the player's hand against the bat c. The force of the ball against the bat d. The weight of the ball e. none of the above 17. A ball is thrown straight up. At the top of its path its instantaneous speed is a. about 5 m/s. b. 0 m/s. c. about 10 m/s. d. about 20 m/s. e. about 50 m/s. 18. A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the speed of the ball when caught would be a. more than the speed it had when thrown upwards. b. less than the speed it had when thrown upwards. c. the same as the speed it had when thrown upwards. 19. An unfortunate bug splatters against the windshield of a moving car. Compared to the force of the car on the bug, the force of the bug on the car is a. smaller. b. larger. c. the same. d. Need more information to say 20. A woman weighing 550 N sits on the floor. She exerts a force on the floor of a. 55 N. b. 1100 N. c. 550 N. d. 5.5 N. e. 5500 N. 21. When representing velocity as a vector, a. the length of the arrow is drawn to a suitable scale. b. the length of the arrow represents the speed. c. the direction of the arrow shows the direction of motion. d. all of the above e. none of the above 22. Acceleration is defined as the CHANGE in a. velocity divided by the time interval. b. time it takes to move from one speed to another speed. c. velocity of an object. d. time it takes to move from one place to another place. e. distance divided by the time interval. 23. When a woman stands with two feet on a scale, the scale reads 280 N. When she lifts one foot, the scale reads a. less than 280 N. b. more than 280 N. c. 280 N. 24. At what part of a path does a projectile have minimum speed? a. At the top of its path b. Halfway to the top c. When it is thrown d. When it returns to the ground e. There's not enough information to say. 25. A ball thrown in the air will never go as far as physics ideally would predict because a. ideally the ball would never land. b. air friction slows the ball. c. one can never throw the ball fast enough. d. gravity is acting. e. all of the above 26. A ball is thrown straight up. At the top of its path its acceleration is a. about 5 m/s 2. b. about 10 m/s 2. c. about 50 m/s 2. d. about 20 m/s 2. e. 0 m/s 2. 27. A scalar is a quantity that has a. magnitude. b. time. c. direction. d. color. 28. The law of inertia states that an object a. will continue moving in a straight line unless an outside force acts on it. b. at rest will remain at rest unless acted on by an outside force. c. that is not moving will never move unless a force acts on it. d. will continue moving at the same velocity unless an outside force acts on it. e. will do all of the above. 29. A 100-N lantern is suspended by a pair of ropes with 120 degrees between them (each 60 degrees from the vertical). The tension in each rope is a. 100 N. b. less than 100 N. c. more than 100 N. 30. A ball is thrown into the air at some angle. At the very top of the ball's path, its velocity is a. entirely vertical. b. There's not enough information given to determine. c. both vertical and horizontal. d. entirely horizontal. 31. A 5-N force and a 30-N force act in the same direction on an object. What is the net force on the object? a. 35 N b. 30 N c. 25 N d. 5 N e. none of the above 2

Name: ID: A 32. A bag of sports equipment has a mass of 10.0 kilograms and a weight of a. 9.8 N. b. 980 N. c. 98 N. d. 0.98 N. e. none of the above 33. Speed is a. the distance covered per unit time. b. always measured in terms of a unit of distance divided by a unit of time. c. a measure of how fast something is moving. d. all of the above. e. none of the above. 34. As a ball falls, the action force is the pull of Earth's mass on the ball. What is the reaction to this force? a. The acceleration of the ball b. Nonexistent in this case c. Air resistance acting against the ball d. The pull of the ball's mass on Earth e. none of the above 35. The mass of a sheep that weighs 110 N is about a. 110 kg. b. 11 kg. c. 1 kg. d. 1100 kg. e. none of the above 36. Which has more mass, a kilogram of feathers or a kilogram of iron? a. The feathers b. The iron c. Neither they both have the same mass. 37. Accelerations are produced by a. accelerations. b. masses. c. forces. d. velocities. e. none of the above 38. A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car s average acceleration? a. 7 m/s 2 b. 0.17 m/s 2 c. 1.67 m/s 2 d. 6 m/s 2 e. none of the above 39. Compared to its weight on Earth, a 10-kg object on the moon will weigh a. the same amount. b. more. c. less. 40. A 20-N falling object encounters 4 N of air resistance. The magnitude of the net force on the object is a. 16 N. b. 20 N. c. 4 N. d. 0 N. e. none of the above 41. In the absence of air resistance, the angle at which a thrown ball will go the farthest is a. 15 degrees. b. 60 degrees. c. 75 degrees. d. 45 degrees. e. 30 degrees. 42. How much force is needed to accelerate a 4.0-kg physics book to an acceleration of 2.0 m/s 2? a. 0.5 N b. 8.0 N c. 24.0 N d. 2.0 N e. 0 N 43. A train travels 6 meters in the first second of travel, 6 meters again during the second second of travel, and 6 meters again during the third second. Its acceleration is a. 0 m/s 2. b. 18 m/s 2. c. 12 m/s 2. d. 6 m/s 2. e. none of the above True/False Indicate whether the statement is true or false. 44. If a hockey puck were to slide on a perfectly frictionless surface, it will eventually slow down because of its inertia. 45. Average speed is defined as the time it takes for a trip divided by the distance. 46. It is possible for an object in free fall to have zero acceleration. 47. A ball is thrown into the air. At the highest point, the ball has zero velocity and zero acceleration. 48. An astronaut weighs the same on Earth as in space. 49. A force can be simply defined as a push or a pull. 50. The SI unit of force is the kilogram. 51. Inertia is the property that every material object has; inertia resists changes in an object's state of motion. 52. Whenever one object exerts a force on another object, the second object always exerts a force back on the first object. 3

Name: ID: A Problem 53. A person weighs 650 N. What is the mass of the person? 54. A 20-kg block of cement is pulled upward (not sideways!) with a force of 400 N. What is the acceleration of the block? 55. Consider an escalator at an angle of 45 above the horizontal that moves with a velocity of 2.0 m/s. What is the horizontal component of the escalator's velocity? 56. An apple falls from a tree and 0.5 second later hits the ground. How fast is the apple falling when it hits the ground? 57. An Olympic skier moving at 20.0 m/s down a 30.0 slope encounters a region of wet snow and slides 145 m before coming to a halt. What is the coefficient of friction between the skis and the snow? (g = 9.81 m/s 2 ) 58. How much (in newtons) does 0.60 kg of salami weigh? 59. A couch with a mass of 1.00 10 2 kg is placed on an adjustable ramp connected to a truck. As one end of the ramp is raised, the couch begins to move downward. If the couch slides down the ramp with an acceleration of 0.70 m/s 2 when the ramp angle is 25.0, what is the coefficient of kinetic friction between the ramp and the couch? (g = 9.81 m/s 2 ) 60. Suppose that you exert 300 N horizontally on a 50-kg crate on a factory floor, where friction between the crate and the floor is 100 N. What is the acceleration of the crate? 61. What engine thrust (in newtons) is required for a rocket of mass 35 kg to leave the launching pad? 62. A bicycle travels 15 km in 30 minutes. What is its average speed? 63. A fighter punches a sheet of paper in midair, and brings it from rest up to a speed of 40 m/s in 0.08 s. What is the force of impact on the paper if the mass of the paper is 0.01 kg? 64. Basking in the sun, a 1.10 kg lizard lies on a flat rock tilted at an angle of 15.0 with respect to the horizontal. What is the magnitude of the normal force exerted by the rock on the lizard? 65. A skateboarder starting from rest accelerates down a ramp at 2 m/s 2 for 2 s. What is the final speed of the skateboarder? 66. A rope attached to an engine pulls a 250 N crate up an 18.0 ramp at constant speed. The coefficient of kinetic friction for the surfaces of the crate and ramp is 0.26. What is the magnitude of the force that the rope exerts on the crate parallel to the ramp? (g = 9.81 m/s 2 ) 67. What is the average acceleration of a car that goes from rest to 60 km/h in 8 seconds? 68. 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? 69. How much time does a car with an acceleration of 5 m/s 2 take to go from 5 m/s to 40 m/s? 70. On the moon, the acceleration due to gravity is 1 that on Earth. What would be the weight of 0.9 kg of bologna on the moon? 6 4

F13--HPhys--Q5 Practice Answer Section MULTIPLE CHOICE 1. ANS: C PTS: 1 DIF: 1 REF: p. 28 OBJ: 3.1 STA: Ph.1.j 2. ANS: C PTS: 1 DIF: 2 REF: p. 46 OBJ: 4.4 STA: Ph.1.b 3. ANS: D PTS: 1 DIF: 2 REF: p. 11 p. 12 OBJ: 2.2 STA: Ph.1.a Ph.1.b 4. ANS: D PTS: 1 DIF: 2 REF: p. 50 5. ANS: A PTS: 1 DIF: 3 REF: p. 77 OBJ: 6.4 STA: Ph.1.d 6. ANS: C PTS: 1 DIF: 2 REF: p. 62 OBJ: 5.3 STA: Ph.1.c 7. ANS: D PTS: 1 DIF: 2 REF: p. 31 p. 32 OBJ: 3.3 STA: Ph.1.j 8. ANS: A PTS: 1 DIF: 1 REF: p. 30 OBJ: 3.2 STA: Ph.1.j 9. ANS: D PTS: 1 DIF: 1 REF: p. 44 OBJ: 4.4 STA: Ph.1.b 10. ANS: C PTS: 1 DIF: 2 REF: p. 15 OBJ: 2.4 STA: Ph.1.c 11. ANS: B PTS: 1 DIF: 2 REF: p. 17 p. 18 p. 19 OBJ: 2.5 STA: Ph.1.b Ph.1.c Ph.2.c 12. ANS: C PTS: 1 DIF: 2 REF: p. 37 p. 38 OBJ: 3.5 STA: Ph.1.f 13. ANS: B PTS: 1 DIF: 1 REF: p. 24 OBJ: 2.8 STA: Ph.1.b Ph.1.c Ph.2.c 14. ANS: C PTS: 1 DIF: 2 REF: p. 44 OBJ: 4.3 STA: Ph.1.b 15. ANS: B PTS: 1 DIF: 3 REF: p. 33 OBJ: 3.4 STA: Ph.1.f 16. ANS: C PTS: 1 DIF: 2 REF: p. 76 OBJ: 6.3 STA: Ph.1.d 17. ANS: B PTS: 1 DIF: 2 REF: p. 18 p. 19 OBJ: 2.5 STA: Ph.1.b Ph.1.c Ph.2.c 18. ANS: C PTS: 1 DIF: 2 REF: p. 18 OBJ: 2.5 STA: Ph.1.b Ph.1.c Ph.2.c 19. ANS: C PTS: 1 DIF: 2 REF: p. 77 OBJ: 6.4 STA: Ph.1.d 20. ANS: C PTS: 1 DIF: 2 REF: p. 75 OBJ: 6.2 STA: Ph.1.d 21. ANS: D PTS: 1 DIF: 2 REF: p. 29 OBJ: 3.2 STA: Ph.1.j 22. ANS: A PTS: 1 DIF: 1 REF: p. 15 OBJ: 2.4 STA: Ph.1.c 23. ANS: C PTS: 1 DIF: 2 REF: p. 65 OBJ: 5.5 STA: Ph.1.c 1

24. ANS: A PTS: 1 DIF: 3 REF: p. 37 OBJ: 3.5 STA: Ph.1.f 25. ANS: B PTS: 1 DIF: 2 REF: p. 37 OBJ: 3.5 STA: Ph.1.f 26. ANS: B PTS: 1 DIF: 3 REF: p. 18 OBJ: 2.5 STA: Ph.1.b Ph.1.c Ph.2.c 27. ANS: A PTS: 1 DIF: 1 REF: p. 29 OBJ: 3.1 STA: Ph.1.j 28. ANS: E PTS: 1 DIF: 1 REF: p. 46 OBJ: 4.4 STA: Ph.1.b 29. ANS: A PTS: 1 DIF: 3 REF: p. 53 OBJ: 4.8 STA: Ph.1.j 30. ANS: D PTS: 1 DIF: 2 REF: p. 36 OBJ: 3.4 STA: Ph.1.f 31. ANS: A PTS: 1 DIF: 2 REF: p. 51 OBJ: 4.6 STA: Ph.1.g Ph.1.l 32. ANS: C PTS: 1 DIF: 2 REF: p. 50 33. ANS: D PTS: 1 DIF: 2 REF: p. 11 p. 12 OBJ: 2.2 STA: Ph.1.a Ph.1.b 34. ANS: D PTS: 1 DIF: 2 REF: p. 76 OBJ: 6.3 STA: Ph.1.d 35. ANS: B PTS: 1 DIF: 2 REF: p. 50 36. ANS: C PTS: 1 DIF: 2 REF: p. 48 p. 49 37. ANS: C PTS: 1 DIF: 1 REF: p. 59 OBJ: 5.1 STA: Ph.1.c 38. ANS: D PTS: 1 DIF: 2 REF: p. 16 OBJ: 2.4 STA: Ph.1.c 39. ANS: C PTS: 1 DIF: 2 REF: p. 49 40. ANS: A PTS: 1 DIF: 2 REF: p. 68 p. 69 OBJ: 5.7 STA: Ph.1.c Ph.2.c 41. ANS: D PTS: 1 DIF: 1 REF: p. 36 OBJ: 3.5 STA: Ph.1.f 42. ANS: B PTS: 1 DIF: 2 REF: p. 62 OBJ: 5.3 STA: Ph.1.c 43. ANS: A PTS: 1 DIF: 2 REF: p. 15 p. 16 OBJ: 2.4 STA: Ph.1.c TRUE/FALSE 44. ANS: F PTS: 1 DIF: 2 REF: p. 47 OBJ: 4.4 STA: Ph.1.b 45. ANS: F PTS: 1 DIF: 1 REF: p. 12 OBJ: 2.2 STA: Ph.1.a Ph.1.b 46. ANS: F PTS: 1 DIF: 2 REF: p. 68 OBJ: 5.6 STA: Ph.1.c Ph.2.c 47. ANS: F PTS: 1 DIF: 3 REF: p. 17 p. 18 OBJ: 2.5 STA: Ph.1.b Ph.1.c Ph.2.c 2

48. ANS: F PTS: 1 DIF: 2 REF: p. 49 49. ANS: T PTS: 1 DIF: 1 REF: p. 44 OBJ: 4.3 STA: Ph.1.b 50. ANS: F PTS: 1 DIF: 1 REF: p. 50 51. ANS: T PTS: 1 DIF: 1 REF: p. 45 OBJ: 4.3 STA: Ph.1.b 52. ANS: T PTS: 1 DIF: 1 REF: p. 74 OBJ: 6.1 STA: Ph.1.b Ph.1.c Ph.1.d PROBLEM 53. ANS: 66 kg PTS: 1 DIF: 2 REF: p. 50 54. ANS: 10 m/s 2 PTS: 1 DIF: 3 REF: p. 68 OBJ: 5.6 STA: Ph.1.c Ph.2.c 55. ANS: 1.4 m/s PTS: 1 DIF: 2 REF: p. 31 OBJ: 3.2 STA: Ph.1.j 56. ANS: 5 m/s PTS: 1 DIF: 3 REF: p. 18 OBJ: 2.6 STA: Ph.1.a Ph.2.c 3

57. ANS: 0.415 Given: v x,i = 20.0 m/s x = 145 m θ = 30.0º g = 9.81 m/s 2 Solution Choose a coordinate system such that the positive x-direction is down the ski slope. The force of friction will be in the negative x-direction. Because ΣF y = 0, = F g,y = mg cos θ = = mg cos θ Ê (v x,i ) 2 ˆ Because v x,f = 0, a x = 2 x Ë Á Ê (v x,i ) 2 ˆ et,x = ma x = m 2 x Ë Á F g,x = F g sin θ = mg sin θ et,x = F g,x = F g,x et,x Ê mg cos θ = mg sin θ m (v ˆ x,i )2 2 x Ë Á = sin θ 2 cos θ (v x,i ) 2g x cos θ = sin 30.0 cos 30.0 (20.0 m/s) 2 2(9.81 m/s 2 )(145 m)(cos 30.0 ) = 0.577 0.162 = 0.415 PTS: 1 DIF: IIIC OBJ: 4-4.4 58. ANS: 5.9 N PTS: 1 DIF: 2 REF: p. 50 4

59. ANS: 0.387 Given m = 1.00 10 2 kg a x = 0.70 m/s 2 θ = 25.0 g = 9.81 m/s 2 Solution ΣF y = F g,y = 0 = F g,y = mg cos θ ΣF x = F g,x = et,x = ma x = F g,x ma x = = mg cos θ F g,x ma x = mg cos θ F g,x = mg sin θ = F g,x ma x mg cos θ = mg sin θ ma x mg cos θ = sin θ cos θ a x g cos θ = sin 25.0 cos 25.0 0.70 m/s 2 = 0.466 0.079 = 0.387 (9.81 m/s 2 )(cos 25.0 ) PTS: 1 DIF: IIIC OBJ: 4-4.4 60. ANS: 4 m/s 2 PTS: 1 DIF: 3 REF: p. 68 OBJ: 5.7 STA: Ph.1.c Ph.2.c 61. ANS: 350 N PTS: 1 DIF: 3 REF: p. 77 OBJ: 6.4 STA: Ph.1.d 62. ANS: 30 km/hr PTS: 1 DIF: 2 REF: p. 11 p. 12 OBJ: 2.2 STA: Ph.1.a Ph.1.b 63. ANS: 5.0 N PTS: 1 DIF: 3 REF: p. 77 OBJ: 6.4 STA: Ph.1.d 5

64. ANS: 10.4 N Given m = 1.10 kg θ = 15.0 g = 9.81 m/s 2 Solution et,y = ΣF y = F g,y = 0 = F g,y = F g cos θ = mg cos θ = (1.10 kg)(9.81 m/s 2 )(cos 15.0 ) = 10.4 N PTS: 1 DIF: IIIA OBJ: 4-4.2 65. ANS: 4 m/s PTS: 1 DIF: 3 REF: p. 15 p. 16 OBJ: 2.4 STA: Ph.1.c 66. ANS: 139 N Given F g = 250 N θ = 18.0 = 0.26 Solution et,y = ΣF y = F g,y = 0 = F g,y = F g cos θ et,x = ΣF x = F applied F g,x = 0 F applied = + F g,x = = F g cos θ = (0.26)(250 N)(cos 18.0 ) = 62 N F g,x = F g sin θ = (250 N)(sin 18.0 ) = 77 N F applied = + F g,x = 62 N + 77 N = 139 N PTS: 1 DIF: IIIB OBJ: 4-4.4 67. ANS: 7.5 km/h s PTS: 1 DIF: 2 REF: p. 16 OBJ: 2.4 STA: Ph.1.c 6

68. ANS: 0.437 m/s 2 Given F applied =128 N θ = 55.0 m 1 = 96.0 kg m 2 = 72.0 kg Solution ΣF x = F applied,x = m T a x F applied,x = F x cos θ m T = m 1 + m 2 a x = F x cos θ (128 N)(cos 55.0 ) 2 = = 0.437 m/s m 1 + m 2 (96.0 kg + 72.0 kg) PTS: 1 DIF: IIIB OBJ: 4-3.2 69. ANS: 7 s PTS: 1 DIF: 3 REF: p. 15 p. 16 OBJ: 2.4 STA: Ph.1.c 70. ANS: 1.5 N PTS: 1 DIF: 3 REF: p. 50 7