AP Physics First Nine Weeks Review

Transcription

1 AP Physics First Nine Weeks Review 1. If F1 is the magnitude of the force exerted by the Earth on a satellite in orbit about the Earth and F2 is the magnitude of the force exerted by the satellite on the Earth, then which of the following is true? A) F1 is much greater than F2. B) F1 is slightly greater than F2. C) F1 is equal to F2. D) F2 is slightly greater than F1. E) F2is much greater than F1. 2. Two blocks are pushed along a horizontal frictionless surface by a force of 20 newtons to the right, as shown above. The force that the 2-kilogram block exerts on the 3- kilogram block is A) 8 newtons to the left B) 8 newtons to the right C) 10 newtons to the left D) 12 newtons to the right E) 20 newtons to the left 3. A horse harnessed to a wagon refuses to pull, citing Newton's third law, which states that for every force there is an equal but opposite reaction force. The horse, incorrect in its reasoning, can pull the wagon because A) after it gives a jerk and the wagon is moving, its pulling force will be greater than the reaction to this force. B) the law applies only to static cases. C) the wagon cannot possibly pull back with a force equal in magnitude to the pulling force. D) the action and reaction forces are acting on different bodies. E) after friction is overcome, the reaction force is less than the pulling force. 4. If an object is moving at uniform speed in a straight line, its instantaneous velocity halfway through any time interval is A) greater than its average velocity. B) less than its average velocity. C) the same as its average velocity. D) half of its average velocity. E) twice its average velocity. Page 1

2 Use the following to answer question 5: 5. The figure represents the parabolic trajectory of a ball going from A to E in earth gravity but without air resistance. What is the direction of the acceleration at point C? A) It is to the right. B) It is to the left. C) It is straight up. D) It is straight down. E) The acceleration of the ball is zero. Page 2

3 6. Which of the following graphs of position d versus t corresponds to motion of an object in a straight line with positive acceleration? A) B) C) D) E) Page 3

4 7. A uniform ladder of weight W leans without slipping against a wall making an angle θ with a floor as shown above. There is friction between the ladder and the floor, but the friction between the ladder and the wall is negligible. the magnitude of the normal force exerted by the floor on the ladder is A) W B) W sinθ C) W cosθ D) W sin θ 2 E) W cosθ 2 8. Two projectiles are launched with the same initial speed from the same location, one at a 30 angle and the other at a 60 angle with the horizontal. They land at the same height at which they were launched. If air resistance is negligible, how do the projectiles' respective maximum heights, H30 and H60, and times in the air, T30 and T60, compare with each other? Maximum Height Time in Air A) H30 > H60 T30 > T60 B) H30 > H60 T30 < T60 C) H30 = H60 T30 = T60 D) H30 < H60 T30 > T60 E) H30 < H60 T30 < T60 Page 4

5 9. The free-body diagram that best represents the forces acting on the student sliding down the incline is A) 1 B) 2 C) 3 D) 4 E) 5 Page 5

6 10. The figure shows a top view of a ball on the end of a string traveling counterclockwise in a circular path. The speed of the ball is constant. If the string should break at the instant shown, the path that the ball would follow is A) 1 B) 2 C) 3 D) 4 E) impossible to tell from the given information. 11. What do acceleration and velocity have in common? A) Both are scalars. B) Both are vectors. C) Both are measured in units of distance divided by time. D) Both are measured in units of distance divided by time squared. E) They are different names for the same quantity. 12. An object is shot vertically upward into the air with a positive initial velocity. Which of the following correctly describes the velocity and acceleration of the object at its maximum elevation? Velocity Acceleration A) Positive Positive B) Zero Zero C) Negative Negative D) Zero Negative E) Positive Negative Page 6

7 13. A ball is thrown and follows a parabolic path, as shown above. Air friction is negligible. Point Q is the highest point on the path. Which of the following best indicates the direction of the acceleration, if any, of the ball at point Q? A) B) C) D) E) There is no acceleration of the ball at point Q. Page 7

8 14. The graph above shows the velocity v as a function of time t for an object moving in a straight line. Which of the following graphs shows the corresponding displacement x as a function of time t for the same interval? A) B) C) D) E) Page 8

9 15. A heavy truck and a light car are traveling at the same speed on the same roadway. If the coefficients of static friction between their tires and the road are the same, which vehicle will be able to stop in the shortest distance? A) the car B) the truck C) Both will be able to stop in the same distance. D) One cannot tell without knowing their coefficients of kinetic friction. E) One cannot tell without knowing their masses. 16. A toy car of mass 6 kg, moving in a straight path, experiences a net force given by the function F = -3t. At time t = 0, the car has a velocity of 4 m/s in the positive direction and is located +8 m from the origin. The car will come instantaneously to rest at time t equal to 2 A) 3 s B) C) 4 3 s 8 3 s D) 8 s E) 4 s 17. What is the least number of non-zero vectors that can be added to give a resultant equal to zero? A) 2 B) 3 C) 4 D) 5 E) It cannot be done. 18. The displacement of an object for a round trip between two locations A) is always greater than zero. B) is always less than zero. C) is zero. D) can be greater than or less than but not equal to zero. E) can have any value. Page 9

10 19. A 500-kilogram sports car accelerates uniformly from rest, reaching a speed of 30 meters per second in 6 seconds. During the 6 seconds, the car has traveled a distance of A) 15 m B) 30 m C) 60 m D) 90 m E) 180 m 20. Which of the following free-body diagrams represents the car going uphill at a constant speed? A) 1 B) 2 C) 3 D) 4 E) 5 Page 10

11 21. A 50-kg block rests on a horizontal surface. The coefficient of static friction µ s = The coefficient of kinetic friction µ k = 0.4. A force P of 300 N is applied as shown. A) The block remains at rest. B) The block moves and continues to move at constant velocity. C) The block accelerates to the right. D) The block does not move until P is increased to greater than 490 N. E) No conclusions can be drawn concerning the movement of the block from the information given. 22. An object moving in a straight line has a velocity v in meters per second that varies with time t in seconds according to the following function. v = t 2 The instantaneous acceleration of the object at t = 2 seconds is A) 2 m/s 2 B) 4 m/s 2 C) 5 m/s 2 D) 6 m/s 2 E) 8 m/s A projectile is fired from the surface of the Earth with a speed of 200 meters per second at an angle of 30 above the horizontal. If the ground is level, what is the maximum height reached by the projectile? A) 5 m B) 10 m C) 500 m D) 1,000 m E) 2,000 m Page 11

12 24. A rock is thrown from the edge of a cliff with an initial velocity v0 at an angle θ with the horizontal as shown above. Point P is the highest point in the rock's trajectory and point Q is level with the starting point. Assume air resistance is negligible. Which of the following correctly describes the horizontal and vertical speeds and the acceleration of the rock at point Q? Horizontal Vertical Speed Speed Acceleration A) v cosθ 0 0 g B) 0 0 g C) v cosθ D) v cosθ v sinθ g 0 0 E) 0 v cosθ In the absence of air friction, an object dropped near the surface of the Earth experiences a constant acceleration of about 9.8 m/s 2. this means that the A) speed of the object increases 9.8 m/s during each second B) speed of the object as it falls is 9.8 m/s C) object falls 9.8 meters during each second D) object falls 9.8 meters during the first second only E) derivative of the distance with respect to time for the object equals 9.8 m/s 2 Page 12

13 26. Several forces act on an object, but the object is in equilibrium. Which of the following statements about the object must be true? I. It has zero acceleration. II. The net force acting on it is zero. III. It is at rest. IV. It is moving with constant velocity. A) I and II B) I and III C) I and IV D) II and III E) II and IV 27. A baseball is thrown with a velocity v at an angle θ with the horizontal. The horizontal component of its velocity in the absence of air resistance is A) v cos θ B) v cos θ gt C) v 2 + 2gx D) v 2 2gx E) v sin θ gt Page 13

14 28. A rock is thrown from the edge of a cliff with an initial velocity v0 at an angle θ with the horizontal as shown above. Point P is the highest point in the rock's trajectory and point Q is level with the starting point. Assume air resistance is negligible. Which of the following correctly describes the horizontal and vertical speeds and the acceleration of the rock at point P? Horizontal Vertical Speed Speed Acceleration A) v cosθ 0 0 g B) 0 0 g C) v cosθ D) v cosθ v sinθ g 0 0 E) 0 v cosθ 0 0 Page 14

15 29. A ball is thrown horizontally from a cliff with a velocity v0. A graph of the acceleration of the ball versus the distance fallen could be represented by curve A) 1 B) 2 C) 3 D) 4 E) 5 Page 15

16 30. A block of mass M1 on a horizontal table is connected to a hanging block of mass M2 by a string that passes over a pulley, as shown above. The acceleration of the blocks is 0.6g. Assume that friction and the mass of the string are negligible. The ratio of masses M2/M1 is A) 0.67 B) 1.0 C) 1.4 D) 1.5 E) A tired worker pushes a heavy (100-kg) crate that is resting on a thick pile carpet. The coefficients of static and kinetic friction are 0.6 and 0.4, respectively. The worker pushes with a force of 500 N. The frictional force exerted by the surface is A) 1000 N B) 600 N C) 500 N D) 400 N E) 100 N Page 16

17 32. A target T lies flat on the ground 3 m from the side of a building that is 10 m tall, as shown above. A student rolls a ball of the horizontal roof of the building in the direction of the target. Air resistance is negligible. The horizontal speed with which the ball must leave the roof if it is to strike the target is most nearly A) 3 10 m/s B) 2 m/s C) 3 2 m/s D) 3 m/s E) m/s Page 17

18 33. A ball initially moves horizontally with velocity vi as shown above. It is then struck by a stick. After leaving the stick, the ball moves vertically with a velocity vf, which is smaller in magnitude than vi. Which of the following vectors best represents the direction of the average force that the stick exerts on the ball? A) B) C) D) E) 34. A spring-loaded gun can fire a projectile to a height h if it is fired straight up. If the same gun is pointed at an angle of 45 from the vertical, what maximum height can now be reached by the projectile? A) h 4 B) h 2 2 C) h 2 D) h 2 E) h Page 18

19 35. A ball is thrown straight up from a point 2 m above the ground. The ball reaches a maximum height of 3 m above its starting point and then falls 5 m to the ground. When the ball strikes the ground, what is its displacement from its starting point? A) Zero B) 8 m below C) 5 m below D) 2 m below E) 3 m above 36. Vectors V1 and V2 shown above have equal magnitudes. The vectors represent the velocities of an object at times t1 and t2, respectively. The average acceleration of the object between time t1 and t2 was A) zero B) directed north C) directed west D) directed north of east E) directed north of west 37. A particle moves along the x-axis with a non-constant acceleration described by a = 12t, where a is in meters per second squared and t is in seconds. If the particle starts from rest so that its speed v and position x are zero when t = 0, where is it located when t = 2 seconds? A) x= 12 m B) x = 16 m C) x = 24 m D) x = 32 m E) x = 48 m Page 19

20 38. An object of mass 100 kg is initially at rest on a horizontal frictionless surface. At time t = 0, a horizontal force of 10 N is applied to the object for 1 s and then removed. Which of the following is true of the object at time t = 2 s if it is still on the surface? A) It is at the same position it had at t = 0, since a force of 10 N is not large enough to move such a massive object. B) It is moving with constant nonzero acceleration. C) It is moving with decreasing acceleration. D) It is moving at a constant speed. E) It has come to rest some distance away from the position it had at t = Two people are in a boat that is capable of a maximum speed of 5 kilometers per hour in still water, and wish to cross a river 1 kilometer wide to a point directly across from their starting point. If the speed of the water in the river is 5 kilometers per hour, how much time is required for the crossing? 1 A) 20 hr 1 B) 10 hr C) 1 hr D) 10 hr E) The point directly across from the starting point cannot be reached under these conditions. 40. A block of mass 5 kilograms lies on an inclined plane, as shown above. The horizontal and vertical supports for the plane have lengths of 4 meters and 3 meters, respectively. The coefficient of friction between the plane and the block is 0.3. The magnitude of the force F necessary to pull the block up the plane with constant speed is most nearly A) 30 N B) 42 N C) 49 N D) 50 N E) 58 N Page 20

21 41. The velocity of a projectile at launch has a horizontal component uh and a vertical component uv. Air resistance is negligible. When the projectile is at the highest point of its trajectory, which of the following show the vertical and horizontal components of its velocity and the vertical component of its acceleration? Vertical Horizontal Vertical Velocity Velocity Acceleration A) uv uh 0 B) uv 0 0 C) 0 uh 0 D) 0 0 g E) 0 uh g 42. A ball is thrown and follows a parabolic path, as shown above. Air friction is negligible. Point Q is the highest point on the path. Which of the following best indicates the direction of the net force on the ball at point P? A) B) C) D) E) Page 21

22 43. A particle of mass m moves along a straight path with a speed v defined by the function 2 v = bt + c, where b and c are constants and t is time. What is the magnitude F of the net force on the particle at time t = t1? 2 A) bt1 + c B) 3mbt1 + 2c C) mbt1 D) mbt1 + c E) 2mbt1 44. A block of mass M1 on a horizontal table is connected to a hanging block of mass M2 by a string that passes over a pulley, as shown above. The acceleration of the blocks is 0.6g. Assume that friction and the mass of the string are negligible. The tension T in the string is A) zero B) 0.4 M2g C) 0.6 M2g D) 1.0 M2g E) 1.6 M2g 45. A physical quantity that is sometimes described as the measure of the resistance of a body to a change in motion is A) force B) mass C) acceleration D) weight E) friction Page 22

23 46. Which of the following pairs of graphs shows the distance traveled versus time and the speed versus time for an object uniformly accelerated from rest at time t = 0? A) B) C) D) E) 47. The position of a toy locomotive moving on a straight track along the x-axis is given by 3 2 the equation x = t 6t + 9t, where x is in meters and t is in seconds. The net force on the locomotive is equal to zero when t is equal to A) zero B) 2 s C) 3 s D) 4 s E) 5 s Page 23

24 48. A uniform ladder of weight W leans without slipping against a wall making an angle θ with a floor as shown above. There is friction between the ladder and the floor, but the friction between the ladder and the wall is negligible. The magnitude of the friction force exerted on the ladder by the floor is A) 2W tanθ B) W C) W cotθ D) W 2 E) W cot θ The relationship between the velocity of a body moving along the x axis and time is given by v = 3t 2 2t, where the units are SI units. The total distance the body travels between the times t = 2 s and t = 4 s is A) 12 m B) 60 m C) 48 m D) 34 m E) 44 m Page 24

25 50. An object moving in a straight line has a velocity v in meters per second that varies with time t in seconds according to the following function. v = t 2 The displacement of the object between t = 0 and t = 6 seconds is A) 22 m B) 28 m C) 40 m D) 42 m E) 60 m 51. At a particular instant, a stationary observer on the ground sees a package falling with speed v1 at an angle to the vertical. To a pilot flying horizontally at constant speed relative to the ground, the package appears to be falling vertically with a speed of v2 at that instant. What is the speed of the pilot relative to the ground? v + v A) 1 2 v v B) 1 2 v v C) 2 1 D) E) v v v + v Page 25

26 52. A toy car of mass 6 kg, moving in a straight path, experiences a net force given by the function F = -3t. At time t = 0, the car has a velocity of 4 m/s in the positive direction and is located +8 m from the origin. Which of the following best shows a graph of position d versus time t for the car? A) B) C) D) E) 53. An object released from rest at time t = 0 slides down a frictionless incline a distance of 1 meter during the first second. The distance traveled by the object during the time interval from t = 1 second to t = 2 seconds is A) 1 m B) 2 m C) 3 m D) 4 m E) 5 m Page 26

27 54. A rock is dropped from the top of a 45-meter tower, and at the same time a ball is thrown from the top of the tower in a horizontal direction. Air resistance is negligible. The ball and the rock hit the level ground a distance of 30 meters apart. The horizontal velocity of the ball thrown was most nearly A) 5 m/s B) 10 m/s C) 14.1 m/s D) 20 m/s E) 28.3 m/s 55. An object is released from rest at time t = 0 and falls through the air, which exerts a resistive force such that the acceleration a of the object is given by a = g bv, where v is the object's speed and b is a constant. If limiting cases for large and small values of t are considered, which of the following is a possible expression for the speed of the object as an explicit function of time? bt A) v = g(1 e ) / b bt B) v = ( ge ) / b C) 2 v = gt bt D) v = ( g + a) t / b v = v + gt, v 0 E) 0 0 Page 27

28 Answer Key 1. C 2. A 3. D 4. C 5. D 6. D 7. A 8. E 9. E 10. B 11. B 12. D 13. C 14. D 15. C 16. E 17. A 18. C 19. D 20. C 21. C 22. A 23. C 24. D 25. A 26. A 27. A 28. A 29. E 30. D 31. C 32. C 33. B 34. C 35. D 36. E 37. B 38. D 39. E 40. B 41. E 42. D 43. E 44. B Page 28

29 45. B 46. E 47. B 48. E 49. E 50. E 51. D 52. E 53. C 54. B 55. A Page 29