PRACTICE TEST for Midterm Exam

Transcription

1 South Pasadena AP Physics PRACTICE TEST for Midterm Exam FORMULAS Name Period Date / / d = vt d = v ot + ½ at d = v o + v t v = v o + at v = v o + ad v = v x + v y = tan 1 v y v v x = v cos v y = v sin x d x = v xt v y = v oy + at d y = v oyt + ½ at v y = v oy + ad y F = ma W = mg P = F A F = mgsin g = 9.8 m/s freq = rev t v = π r (freq) a C = v r F C = mv r π = 3.14 F G = G mm r F S μ S N F K = μ K F N G = N m /kg p = mv I = p = m(v v 0) = Ft p before = p after KE = ½ mv PE = mgh W = F d = KE P = W t KE = ½ mv IMA = Fout F in = din d out AMA = Fout-actual F in-actual Eff = AMA IMA 100% PEbefore + KEbefore = PEafter + KEafter Use these terms to identify each description given in terms 1-1 below: Acceleration Centripetal Acceleration Centripetal Force Coefficient of Friction Displacement Distance Energy Force Force of Friction Frequency Gravitational Force Gravitational Potential Energy Impulse Kinetic Energy Mass Momentum Normal Force Position Power Pressure Speed Tension Time Velocity Weight Work

2 Description Quantity Vector/Scalar Units A push or pull perpendicular to an object s motion. The attraction between two objects due to their masses. The change in an object s kinetic energy. The duration of an object s motion. Centripetal force Vector N or kg m s Gravitational Force Vector N or kg m s Work Scalar J or kg m s Time Scalar s 5 The force exerted over an area. Pressure Vector Pa or kg m s 6 The force exerted over time. Impulse Vector N s or kg m s 7 The pull exerted on a string or rope. Tension Vector N or kg m s 8 The rate at which an object s velocity changes. Acceleration Vector m s 9 The rate at which momentum changes. Force Vector N or kg m s 10 The rate of change of an object s position. Velocity Vector m s 11 The stored energy of an object due to its height. Gravitational Potential Energy Scalar J or kg m s 1 The total length traveled by an object. Distance Scalar m Kinematics: Motion in One-Dimension 1. How long would it take a car, starting from rest and accelerating uniformly in a straight line at 5 m/s, to cover a distance of 00 m? a) 9.0 s c) 1.0 s b) 10.5 s d) 15.5 s. A kg rubber ball is thrown downward from the top of a building 30-m building with a speed of 4.0 m/s. How high above the ground is the ball after.0 s? a).4 m d).0 m b) 8.0 m e) 7.6 m c) 1. m

3 3. Which of the following statements are about uniformly accelerated motion? Select two answers. a) If an object s acceleration is constant then it must move in a straight line. b) If an object s acceleration is zero, then it s speed must remain constant. c) If an object s speed remains constant, then its acceleration must be zero. d) If the object s direction of motion is changing then its acceleration is not zero. 3 Kinematics in Two Dimensions (Projectile Motion & Vectors) 7. A ball was pitched with a speed of 40 m/s at an angle of 35 to the ground. What is the vertical component of the velocity of the ball? a) 3 m/s d) 49 m/s b) 33 m/s e) 70 m/s c) 40 m/s Questions 8-10: A football is kicked with a horizontal velocity of 0 m/s and a vertical velocity of 15 m/s. 4. On a horizontal number line, a fly is at the coordinate +6. The fly then flies and lands at the coordinate of. If the time traveled by the fly is 4 s, what is the fly s velocity? a).0 units/s b) 1.0 unit/s c) 0.50 units/s d) 1.0 unit/s e).0 units/s 5. A tennis ball is tossed vertically from the ground with a speed of 30 m/s. With what speed will the ball hit the ground? a) 0 m/s d) 30 m/s b) 10 m/s e) 40 m/s c) 0 m/s 8. What is the speed of the ball when it reaches its peak? a) 0 m/s d) 5 m/s b) 15 m/s e) 35 m/s c) 0 m/s 9. What is the speed of the ball when it returns to the ground? a) 0 m/s d) 5 m/s b) 15 m/s e) 35 m/s c) 0 m/s 6. At a particular time, an object is moving with a velocity of 0 m/s and an acceleration of 0 m/s. Which of the following is true about the object s motion? a) It is not moving. b) It is speeding up (accelerating). c) It is slowing down (decelerating). d) Its speed is not changing. e) It is both speeding up and slowing down. 10. How long does the ball travel in the air? a) 1.5 s d) 5 s b) 3 s e) 6 s c) 4 s * * * * * * * * * * * * * * * * * * * * * * * *

4 11. A stone is thrown horizontally with an initial speed of 30 m/s from a bridge. Find the stone s total speed when it enters the water 4 seconds later. (Ignore air resistance.) a) 30 m/s c) 50 m/s b) 40 m/s d) 60 m/s 1. A soccer ball, at rest on the ground, is kicked with an initial velocity of 10 m/s at a launch angle of 30. Calculate its total flight time, assuming that air resistance is negligible. a) 0.5 s c) s b) 1 s d) 4 s 13. Which one of the following statements is true concerning the motion of an ideal projectile launched at an angle of 45 to the horizontal? a) The acceleration vector points opposite to the velocity vector on the way up and in the same direction as the velocity vector on the way down. b) The speed at the top of the trajectory is zero. c) The object s total speed remains constant during the entire flight. d) The vertical speed decreases on the way up and increases on the way down. 4 Motion and Force: Dynamics (Newton s Three Laws of Motion) 14. A force of x newtons is applied to a crate on a frictionless surface, and the crate accelerates at.0 m/s. What force (in newtons) should be applied for the crate to accelerate at 8.0 m/s? a) 0.5x b) x c) x d) 3x e) 4x 15. A 100-kg anchor is dropped in the water and falls at a constant speed of 4.5 m/s. What is the force of the resistance of the water encountered by the anchor? a) 10. N d) 530 N b). N e) 980 N c) 450 N 16. A ball is released and rolls down a rough ramp with an acceleration of 3.5 m/s. Which of these forces is NOT acting on the ball? a) The weight of the ball. b) The force of the ramp pushing on the ball. c) The force of friction between the ball and the ramp. d) The force of the push. e) All of the above act on the ball. 17. A person standing on a horizontal floor feels two forces: the downward pull of gravity and the upward supporting force from the floor. These two forces a) have equal magnitudes and form an action/reaction pair. b) have equal magnitudes but do not form an action/reaction pair. c) have unequal magnitudes and form an action/reaction pair. d) have unequal magnitudes and do not form an action/reaction pair. 18. A person who weighs 800 N steps onto a scale that is on the floor of an elevator car. If the elevator accelerates upward at a rate of 5 m/s, what will the scale read? a) 400 N c) 1000 N b) 800 N d) 100 N

5 19. A frictionless inclined plane of length 0 m has a maximum vertical height of 5 m. If an object of mass kg is placed on the plane, which of the following best approximates the net force it feels? 3. Assuming a frictionless, mass-less pulley, determine the acceleration of the blocks once they are released from rest. a) 5 N c) 15 N b) 10 N d) 0 N 0. A 0 N block is being pushed across a horizontal table by an 18 N force. If the coefficient of kinetic friction between the block and the table is 0.4, find the acceleration of the block. a) 0.5 m/s c) 5 m/s b) 1 m/s d) 7.5 m/s 1. The coefficient of static friction between a box and a ramp is 0.5. The ramp s incline angle is 30. If the box is placed at rest on the ramp, the box will do which of the following? a) Accelerate down the ramp. m a) m g M + m b) M g m c) (M + m) g (M m) d) (M m) g (M + m) M b) Accelerate briefly down the ramp but then slow down and stop. c) Move with constant velocity down the ramp. d) Not move.. If all of the forces acting on an object balance so that the net force is zero, then a) the object must be at rest. b) the object s speed will decrease. c) the object s direction of motion can change, but not its speed. d) None of the above will occur. 4. A block of mass m is at rest on a frictionless, horizontal table placed in a laboratory on the surface of the Earth. An identical block is at rest on a frictionless horizontal table placed on the surface of the Moon. Let F be the net force necessary to give the Earth bound block an acceleration of a across the table. Given that g Moon is one-sixth of g Earth, the force necessary to give the Moon bound block the same acceleration a across the table is a) F/6 c) F b) F/3 d) 6 F 5. A force F of strength 0 N acts on an object of mass 3 kg as it moves a distance of 4 m. If F is perpendicular to the 4 m displacement, the work it does is equal to a) 0 J c) 80 J b) 60 J d) 600 J

6 6. Under the influence of a force, an object of mass 4 kg accelerates from 3 m/s to 6 m/s in 8 s. How much work was done on the object during this time? a) 7 J c) 7 J b) 54 J d) 96 J 5 Circular Motion and Law of Gravitation 7. A 0.80-kg rubber stopper is connected to a string and makes a circular path. Which of the following requires the greatest tension on the string? (v = speed of the rubber stopper; r = radius of the circular path) a) v = 6.0 m/s r = 0.40 m b) v = 6.0 m/s r = 0.80 m c) v = 9.0 m/s r = 0.60 m d) v = 1.0 m/s r = 0.40 m e) v = 1.0 m/s r = 0.80 m 8. A person s weight is the same on Titan (one of Saturn s moons) as on Europa (one of Jupiter s moons). However, Europa s radius is half that of Titan s. If the Europa has a mass of m kg, what is Titan s mass? a) 0.5m d) m b) 0.50m e) 4m c) m 9. When a car is banking a curve (assuming circular motion), which of the following is pointed in the same direction as the friction between the tires and the road? I. Centripetal Acceleration II. III. a) I only. b) II only. c) III only. d) I and II only. e) I, II, and III. Centripetal Force Instantaneous Velocity (The Next Five Questions Are From the Chapter 5 Practice Test) 30. A ball is connected to a string and makes a circular path. The tension on the string (which is the centripetal force) is 6.0 N. If the radius remains constant and the velocity doubles, what will be the new tension on the string? a) 1.5 N d) 1 N b) 3.0 N e) 4 N c) 6.0 N 31. A 0.00 kg rubber stopper is attached to one end of a string that is passed through a plastic tube. At the other end of the string weights are attached. A student whirls the rubber stopper in a horizontal circular path at constant speed, making ten revolutions every 4 seconds. If the radius of the circular path is 0.50 m, what is the centripetal acceleration acting on the stopper? a)0.16 m/s d) 1.5 m/s b).5 m/s e) 13 m/s c) 5.0 m/s 3. If an object moves with a frequency of 1 revolutions per minute, how many seconds does it take to make three revolutions? a) 9 d) 4 b) 1 e) 36 c) A 500 g toy train (as shown below) completes 10 laps of its circular track in 1 minute and 40 seconds. If the diameter of the track is 1 meter, find the train s (a) centripetal acceleration, a c = m/s (b) centripetal force, F c = N (c) period, T = 10 s (d) frequency, f = 0.1 Hz

7 34. Alan makes 38 complete revolutions on the playground Round-A-Bout in 30 seconds. If the radius of the Round-A-Bout is 1meter, determine the (a) Period of the motion, T = s (b) Frequency of the motion, f = 1.7 Hz 37. While a person lifts a book of mass kg from the floor to a tabletop, 1.5 m above the floor, how much work does the gravitational force do on the book? a) 30 J c) 0 J b) 15 J d) 15 J (c) Linear speed at which Alan revolves = 7.96 m/s (d) Centripetal force on 40 kg Alan = 530 N 38. A block of mass 3.5 kg slides down a frictionless inclined plane of length 6.4 m that makes an angle of 30 with the horizontal. If the block is released from rest at the top of the incline, what is its speed at the bottom? a) 5.0 m/s c) 8.0 m/s b) 6.4 m/s d) 10 m/s 39. An astronaut drops a rock from the top of a crater on the Moon. When the rock is halfway down to the bottom of the crater, its speed is what fraction of its final impact speed? a) 1/4 c) 1/ 6 Work and Energy 35. A.5-kg box is pushed across a surface with a force of.0 N at a constant speed of 1.5 m/s. What is the coefficient of kinetic friction between the box and the surface? a\ b) 0.53 c) 0.80 d) 1.3 b) 1/ d) 1/ 40. A force of 00 N is required to keep an object sliding at a constant speed of m/s across a rough floor. How much power is being expended to maintain this motion? a) 50 W c) 00 W b) 100 W d) 400 W e) A box of mass m slides down a frictionless inclined plane of length L and vertical height h. What is the change in its gravitational potential energy? a) m g L c) m g L/h b) m g h d) m g h/l 41. A.5-kg box is pushed across a surface with a force of.0 N at a constant speed of 1.5 m/s. What is the coefficient of kinetic friction between the box and the surface? a) d) 1.3 b) 0.53 e) 1.9 c) 0.80

8 4. Two identical cars (they have the same mass) are driving on a freeway. One is traveling at 7 mph, while the other one is traveling at 3 mph. What is the ratio of the kinetic energy of the first car to that of the second car? a) d).5 b) e) 5.0 c) A delivery man carries a 5.0-kg box up a flight of stairs 4.0 m above the ground. How much work was done on the box by the man? a) 0 J d) 98 J b) 0 J e) 196 J c) 49 J 44. A 57-g tennis ball was dropped from a height of.0 m. If it bounces back up to a height of 1.8 m, how much energy was transferred when it hit the ground? a) 0 J d) 0.56 J b) J e) 1.0 J c) 0.11 J 45. A pulley system lifts a 0-kg box 1.5 m into the air. If 6.0 m of rope was pulled, what was the tension on the string? a) 5.0 N d) 196 N b) 49 N e) 784 N c) 80 N 7 Linear Momentum Chapter 7 will have the greatest number of questions since no test on Chapter 7 will be given before the Midterm and so more practice is needed. 46. A hammer that hits a nail with a 150 N force delivers an impulse of 0.75 N s. How long did the hammer make contact with the nail? a) s d).0 s b) 0.00 s e) 00 s c) 0.50 s 47. A force of 15 N was applied to a 5.0 kg ball so it accelerates from.0 m/s to 8.0 m/s. How long was this force applied? a) 0.50 s d) 3.0 s b).0 s e) 6.0 s c).5 s 48. Ball A has a mass of.0 kg and is rolling across a smooth surface. If Ball B is moving twice as fast as Ball A, but has the same momentum, what is Ball B s mass? a) 0.50 kg b) 1.0 kg c).0 kg d) 4.0 kg e) Not enough information to determine. 49. A car of a train moves at a constant speed of 0 m/s toward another identical car that is at rest. If the two cars lock together when they collide, what will be the speed that the two cars will move? a) 0 m/s d) 30 m/s b) 10 m/s e) 40 m/s c) 0 m/s 50. A boy delivers a 0.7 N s impulse on a 1.-kg toy train by pushing it for 5.0 s. If the toy train s initial velocity was 0.60 m/s, what s the final momentum of the train? a) 0.60 N s d) 1.44 N s b) 0.7 N s e) 3.00 N s c) 1.0 N s 51. An object rolling at a constant speed has a momentum of 60 N s. If the mass of the object is doubled and the speed is tripled, what is the new momentum? a) 10 N s d) 10 N s b) 30 N s e) 360 N s c) 60 N s

9 5. When a porcelain bowl is dropped 1 m on a padded mat, it does not break. Which of these is smaller compared to dropping it on the hard ground? I. The impulse. II. The speed of the bowl. III. The force of impact. a) I only. b) II only. c) III only. d) I and III only. e) I, II, and III. 53. Runner A is moving at 3 m/s and Runner B is moving at 6 m/s. If the two runners have the same momentum, and Runner A has a mass of x kg, what is the mass of Runner B in kg? a) 0.33x b) 0.50x c).0x d) 3.0x e) 6.0x 54. A particle is moving at a constant speed in a circular path. The momentum vector is pointing: a) Curved along the path of the circle. b) Inward, toward the center of the circle. c) Outward, away from the center of the circle. d) Tangent to the circle, in the direction of the motion. e) Tangent to the circle opposite to the direction of motion. 55. The units for impulse are: a) kg m s b) kg m s 1 c) kg m s d) kg m 1 s e) kg m s 56. When a force of 30 N is applied to each of the following, which will require the most time to stop? a) m = 30 kg v = 1 m/s b) m = 30 kg v = 4 m/s c) m = 45 kg v = 18 m/s d) m = 60 kg v = 1 m/s e) m = 60 kg v = 4 m/s 57. A force is applied to a block over a period of 6 seconds. The graph is shown below. What is the impulse from t = 0 s to t = 3 s? Force (N) a) 3.3 N s d) 30 N s b) 10 N s e) 45 N s c) 15 N s 58. A 0-N force is applied for 3 s against a 15-kg ball moving at 5 m/s to slow it down. What is the final speed of the ball? a) 0.50 m/s d).0 m/s b) 1.0 m/s e).5 m/s c) 1.5 m/s Time (s)

10 59. A 5.0-kg ball is dropped from the top of a balcony for 3.0 s. Approximately what is the impulse on the ball over this time? a) 15 N s b) 30 N s c) 50 N s d) 75 N s e) 150 N s 60. Which of the following is true for an inelastic collision? I. After the collision, the collided objects move together as one object. II. III. a) I only. b) II only. c) III only. There is a loss of energy for the system during the collision. There is a loss of momentum for the system during the collision. d) I and II only. e) I, II, and III. 61. Ball A, which has a mass of 1.0 kg, moves with a velocity of +1.5 m/s. It collides elastically with Ball B, which has a mass of 0.50 kg and is at rest. If Ball A comes to a rest after the collision, what is the final velocity of Ball B? a) 0 m/s b) 0.75 m/s c) 1.0 m/s d).0 m/s e) 3.0 m/s 6. Jon, who has a mass of 60 kg, runs 1.0 m/s eastward and collides with Peter, who has a mass of 80 kg and is at rest. After the inelastic collision, a) Both Jon and Peter will move eastward at a speed less than 1.0 m/s. b) Both Jon and Peter will move eastward at a speed of 1.0 m/s. c) Both Jon and Peter will move eastward at a speed greater than 1.0 m/s. d) Jon will stop moving, while Peter will move eastward at a speed less than 1.0 m/s. e) Jon will fall westward, while Peter will move eastward at 1.0 m/s. 63. A kg bullet is shot from a 5.0 kg rifle. If the bullet travels at 80 m/s, what is the recoil velocity of the rifle? a) m/s b) m/s c) m/s d) 0.80 m/s e) 10 m/s 64. Ball A has a mass of.0 kg and Ball B has a mass of 4.0 kg. When the two balls collide elastically, which of the following is NOT true? a) The force of Ball A hitting Ball B is equal to in magnitude as the force of the Ball B hitting Ball A. b) The impulse of the collision is zero. c) The net force on the system is zero. d) The sum of the velocities of the balls before the collision is equal to that after the collision. e) The total momentum of both balls before the collision is equal to that after the collision.

11 The Midterm Exam will not have any Free Response Questions, however, solving these Free Response Questions that follow will be helpful to your studying! Describe the object s motion from t = 0 s to t = 6 s. ( points) From t = 0 to t =, the object is moving at a constant speed of 3 m/s. From t = to t = 6, the object is moving with constant acceleration from 3 m/s to 6 m/s. Free Response Please show all work neatly with units for computational problems Answers should be recorded with the appropriate number of significant figures, the correct direction (+ or, if applicable), and units. Any responses without adequate work would not be given full credit for a Unit Exam. Free Response Answers Please show all work neatly for computational problems (I.E.S.A.). Answers should be recorded with the appropriate number of significant figures, the correct direction (+ or, if applicable), and units. Any responses without adequate work would not be given full credit. Chapter : Motion in 1D 1. An object is moving in along a straight line according to velocity vs. time graph below. Every interval along the x-axis represents 1 s, and every interval along the y-axis represents 1 m/s.. A foam ball is launched from the ground straight up with a velocity of 40 m/s. What is the ball s velocity after 6. s? (4 points) t = 6. s v = v 0 + at = (40 m/s) + ( 9.8 m/s )(6. s) = 0.8 m/s v 0 = 40 m/s v =? a = 9.8 m/s Chapter 3: Motion in D 3. A cannon ball is fired with a horizontal velocity of 6.0 m/s and a vertical velocity of.5 m/s. (a) What is the initial velocity with which the cannonball was fired? ( points) v x = 6.0 m/s v = v x + v y = (6.0 m/s) + (.5 m/s) = 6.5 m/s v y =.5 m/s v =? velocity time (b) After how many seconds will the ball return to the ground? (4 points) t =? d y = v 0yt + ½ at d y = 0 m (0 m) = (.5 m/s)(t) + ½ ( 9.8 m/s )(t ) v 0y =.5 m/s t = 0.51 s a = 9.8 m/s

12 Chapter 4: Forces 4. In the setup shown, box A has a mass of 0.30 kg and box B has a mass of 0.05 kg. Assume no friction. (a) Draw the free body diagram for this system. ( points) A N W A T B T W B Chapter 5: Circular Motion 5. A kg mass is tied to a 0.60-m string and swung to make a circular orbit. (a) If the tension on the string is 0.0 N, what is the speed with which the mass travels? (4 points) F C = 0.0 N F C = mv r m = kg (0.0 (0.150 kg)v N) = (0.60 m) v =? v = 8.9 m/s r = 0.60 m (b) What is the acceleration with which this system moves? (4 points) m A = 0.30 kg F net = m sys a sys m B = 0.05 kg W B T + T = (m A + m B)(a sys) W A = m Ag = (0.30 kg)(9.8 m/s ) =.94 N (0.45 N) = (0.30 kg kg)(a sys) W B = m Bg = (0.05 kg)(9.8 m/s ) = 0.45 N a = m/s (b) Draw the vector that represents the path of the mass if the string was let go. ( points)

13 Chapter 6: Energy 6. A kg soccer ball was kicked from the ground with an initial speed of 3.5 m/s. (a) Find the maximum height if it is moving at 1.5 m/s at that point. (4 points) Before KE after After PE before + KE before = PE after + m = kg m = kg 1 mv = mgh h = 0 m h =? 1 (0.400 kg)(3.5 m/s) = (0.400 kg)(9.8 m/s )h v = 3.5 m/s v = 0 m/s h = 53.9 m (b) Why is the ball traveling slower at the height of its path? Explain briefly using energy arguments. ( points) At the height of the path, all the kinetic energy at the beginning has been converted to potential energy. With less kinetic energy, it travels at a slower speed. Chapter 7: Momentum 7. A 1500-kg car traveling at 15 m/s collides inelastically with a 3500-kg pick-up truck at rest. (a) With what speed to the vehicles move after the collision? (4 points) Before After p before = p after m 1 = 1500 kg m 1 = 1500 kg m 1v 1 + m v = (m 1 + m )v v 1 = 15 m/s m = 3500 kg (1500 kg)(15 m/s) + (3500 kg)(0 m/s) = (1500 kg kg)v m = 3500 kg V =? v = 4.5 m/s v = 0 m/s (b) If time of impact of the collision was.0 s, what force was experienced by the pick-up truck? (4 points) m = 3500 kg J = p = m(v v 0) = Ft v 0 = 0 m/s (3500 kg)(4.5 m/s 0 m/s) = (F)(.0 s) v = 4.5 m/s F = 7875 N F =? t =.0 s