Practice problems for chapter 5 6- PHYS PDF

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If you know how to solve these questions you are ready for the exams, so solve these problems before taking the exam....

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Practice Problem Set 1- PHYS 121- WITH KEY Chapters: 5 24) General Questions: A box is placed on a table which rests on the floor. The box pushes on the table; the reaction force to the box's push on the table is the table's push on the floor. A) True B) False Answer: B Topic: General Questions

25--26) ,… 27) General Questions: An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be A) greater than the weight of the elevator. B) less than than the weight of the elevator. C) equal to the weight of the elevator. Answer: A Topic: General Questions

28) General Questions: A bucket is being lowered by a very light rope with a constant downward velocity. The tension in the rope must be A) equal to the weight of the bucket. B) greater than the weight of the bucket. C) less than the weight of the bucket. Answer: A Topic: General Questions

29) General Questions: Bill and his daughter Susan are both standing on identical skateboards (with really good frictionless ball bearings), initially at rest. Bill weighs three times as much as Susan. Bill pushes horizontally on Susan's back, causing Susan to start moving away from Bill. Just after Bill stops pushing, A) Susan and Bill are moving away from each other, and Susan's speed is three times that of Bill. B) Susan is moving away from Bill, and Bill is stationary. C) Susan and Bill are moving away from each other, with equal speeds. D) Susan and Bill are moving away from each other, and Susan's speed is one-third that of Bill. Answer: A Topic: General Questions

30) General Questions: You push on box G that is next to box H, causing both boxes to slide along the floor, as shown in the figure. The reaction force to your push is

A) the push of box G on box H. B) the push of box H on box G. C) the push of box G against you. D) the upward force of the floor n box G. E) the acceleration of box G. Answer: C Topic: General Questions

31) General Questions: An object is moving with constant non-zero velocity. Which of the following statements about it must be true? A) A constant force is being applied to it in the direction of motion. B) A constant force is being applied to it in the direction opposite of motion. C) A constant force is being applied to it perpendicular to the direction of motion. D) The net force on the object is zero. E) Its acceleration is in the same direction as it velocity. Answer: D Topic: General Questions

32) General Questions: A truck is using a hook to tow a car whose mass is one quarter that of the truck. If the force exerted by the truck on the car is 6000 N, then the force exerted by the car on the truck is A) 1500 N. B) 24,000 N. C) 6000 N. D) 12,000 N. E) We need to know if the car is accelerating to answer this question. Answer: C Topic: General Questions

33) General Questions: A golf club hits a golf ball with a force of 2400 N, sending the ball into the air. The force exerted on the club by the ball must be less than 2400 N or else the ball would not have moved forward. A) True B) False C) The answer depends on whether the golfer followed through with the swing. Answer: B Topic: General Questions

34) General Questions: The figure shows two boxes, with m1 > m2, that are on a level frictionless surface. We can apply a horizontal force

either toward the right on m1 or toward

the left on m2. The magnitude of the force that the boxes exert on each other is

A) zero newtons in either case. B) larger if

is applied toward the right.

C) larger if is applied toward the left. D) the same in either case. Answer: C Topic: General Questions

35) General Questions: An object of mass m rests on a flat table. The earth pulls on this object with a force of magnitude mg. What is the reaction force to this pull? A) The table pushing up on the object with force mg. B) The object pushing down on the table with force mg. C) The table pushing down on the floor with force mg. D) The object pulling upward on the Earth with force mg. E) The table pulling upward on the Earth with force mg. Answer: D Topic: General Questions

36) General Questions: A person is using a rope to lower a 5.0-N bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket? A) 0.00 N B) 2.0 N C) 5.0 N D) 10 N E) 49 N Answer: C Topic: General Questions

37) General Questions: A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what would the scale read?

A) more than 700 N B) less than 700 N C) 700 N D) It could be more or less than 700 N, depending on whether the elevator is going up or down. Answer: C Topic: General Questions

38) Newton's Second Law in 1 Dimension: When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.) A) The elevator is accelerating upward at a constant rate. B) The elevator is accelerating downward at a constant rate. C) The elevator is moving upward at a constant rate. D) The elevator is moving downward at a constant rate. E) From the given information, we cannot tell if the elevator is moving up or down. Answer: B, E Topic: Newton's Second Law in 1 Dimension

39) ---

40) Equilibrium: Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same.

Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block, A?

A)

B)

C)

D)

E)

Answer: E Topic: Equilibrium

41) Equilibrium: As shown in the figure, a woman is straining to lift a large crate, but without success because it is too heavy. We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person, C is the magnitude of the vertical contact force on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

A) P + C = W B) P + C < W C) P + C > W D) P = C Answer: A Topic: Equilibrium

42) Equilibrium: A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The friction force on the box due to the floor is equal to

A) P sin θ. B) P cos θ. C) 0. D) P cos θ + W. E) P + W. Answer: B Topic: Equilibrium

43) … 44) Multiple-Object Accelerating Systems: Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

A) zero. B) less than F but not zero. C) equal to F. D) greater than F. Answer: B Topic: Multiple-Object Accelerating Systems

45) Multiple-Object Accelerating Systems: Two objects of unequal masses, M and m (M > m), are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, and friction is negligible.

Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

A)

B)

C)

D)

Answer: C 46) Slanting Surfaces Without Friction: A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled? A) 200 N B) 120 N C) 160 N D) 150 N E) 0 N Answer: C Topic: Slanting Surfaces Without Friction

47) Slanting Surfaces With Friction: A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about force of static friction f on the block? A) f > mg B) f > mg cos θ C) f > mg sin θ D) f = mg cos θ E) f = mg sin θ Answer: E Topic: Slanting Surfaces With Friction

48) Uniform Circular Motion: You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it A) moves along a straight-line path away from the center of the circle. B) moves along a straight-line path toward the center of the circle. C) moves along a straight-line path in its original direction. D) continues to follow a circular path, but with a radius larger than the original radius. E) moves along a path that is neither straight nor circular.

Answer: C Topic: Uniform Circular Motion

49) Banked Curves: When a car goes around a banked circular curve at the proper speed speed for the banking angle, what force cause it to follow the circular path? A) the normal force from the road B) the friction force from the road C) gravity D) No force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration. Answer: A Topic: Banked Curves

50) Mass and Weight: What is the mass of an object that experiences a gravitational force of 685 N near Earth's surface where g = 9.80 m/s2? A) 69.9 kg B) 68.5 kg C) 71.3 kg D) 72.7 kg Answer: A Topic: Mass and Weight

51) Newton's Second Law in 1 Dimension: A net force of 125 N is applied to a certain object. As a result, the object accelerates with an acceleration of 24.0 m/s2. The mass of the object is A) 3000 kg. B) 2880 kg. C) 144 kg. D) 0.200 kg. E) 5.21 kg. Answer: E Topic: Newton's Second Law in 1 Dimension

52) Newton's Second Law in 1 Dimension: A block is on a frictionless table, on earth. The block accelerates at 5.3 m/s2 when a 10 N horizontal force is applied to it. The block and table are set up on the Moon where the acceleration due to gravity is 1.62 m/s2. A horizontal force of 5 N is now applied to the block when it is on the Moon. The acceleration imparted to the block by this force is closest to A) 2.7 m/s2. B) 2.4 m/s2. C) 2.9 m/s2. D) 3.2 m/s2. E) 3.4 m/s2. Answer: A Topic: Newton's Second Law in 1 Dimension

53) Newton's Second Law in 1 Dimension: On its own, a tow truck has a maximum acceleration

of 3.0 m/s2. What will be its maximum acceleration when the truck is using a light horizontal chain to tow a bus of twice its own mass? A) 2.5 m/s2 B) 2.0 m/s2 C) 1.5 m/s2 D) 1.0 m/s2 Answer: D Topic: Newton's Second Law in 1 Dimension

54) Newton's Second Law in 1 Dimension: A certain aircraft has a mass of 300,000 kg. At a certain instant during its landing, its speed is 27.0 m/s. If the braking force is a constant 445,000 N, what is the speed of the airplane 10.0 s later? A) 10.0 m/s B) 12.2 m/s C) 14.0 m/s D) 18.0 m/s E) 20.0 m/s Answer: B Topic: Newton's Second Law in 1 Dimension

55) Newton's Second Law in 1 Dimension: In a certain particle accelerator, a proton reaches an acceleration of 9.0 × 1013 m/s2. The mass of a proton is 1.67 × 10-27 kg. What is the force on the proton? Answer: 1.5 × 10-13 N Topic: Newton's Second Law in 1 Dimension

56) Newton's Second Law in 1 Dimension: Calculate the average force a bumper would have to exert to bring a 1200-kg car to rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph). A) 1.8 × 104 N B) 1.6 × 104 N C) 5.4 × 104 N D) 6.5 × 105 N E) 3.2 × 104 N Answer: B Topic: Newton's Second Law in 1 Dimension

57) Newton's Second Law in 1 Dimension: The figure shows an acceleration-versus-force graph for a 125-g object. What should be the value of the first tick-mark on the vertical scale, as indicated by the arrow in the figure?

A) 4 B) 8 C) 0.00400 D) 0.00800 Answer: A Topic: Newton's Second Law in 1 Dimension

58) Newton's Second Law in 2 Dimensions: A 1000-kg barge is being towed by means of two horizontal cables. One cable is pulling with a force of 80.0 N in a direction 30.0° west of north. In what direction should the second cable pull so that the barge will accelerate northward, if the force exerted by the cable is 120 N? Assume that the water exerts no appreciable frictional drag on the barge. A) 19.5° east of north B) 21.1° east of north C) 39.0° east of north D) 47.5° east of north E) 54.7° east of north Answer: A Topic: Newton's Second Law in 2 Dimensions

59) Equilibrium: A tightrope walker walks across a 30-m long wire tied between two poles. The center of the wire is displaced vertically downward by 1.0 m when he is halfway across. If the tension in both halves of the wire at this point is 6294 N, what is the mass of the tightrope walker? Neglect the mass of the wire. A) 85 kg B) 43 kg C) 74 kg D) 91 kg Answer: A Topic: Equilibrium

60) Equilibrium: A piano mover raises a 1000-N piano at a constant speed using a very light rope

in a frictionless pulley system, as shown in the figure. With what force is the mover pulling down on the rope?

A) 2000 N B) 1000 N C) 500 N D) 250 N E) Depends on the speed of the piano. Answer: C Topic: Equilibrium

61) Equilibrium: A 6.00-kg ornament is held at rest by two light wires that form 30° angles with the vertical, as shown in the figure. An external force of magnitude F acts vertically downward on the ornament. The tension exerted by each of the two wires is denoted by T. A free-body diagram, showing the four forces that act on the box, is shown in the figure. If the magnitude of force F is 410 N, what is the magnitude of the tension T?

A) 271 N B) 235 N C) 188 N D) 376 N E) 470 N Answer: A Topic: Equilibrium

62) Equilibrium: A 10.0-kg picture is held in place by two wires, the first one hanging at 50.0° to the left of the vertical and the second one at 45.0° to the right of the vertical. What is the tension in the first wire? A) 69.6 N B) 50.8 N C) 98.1 N D) 69.4 N E) 23.8 N Answer: A Topic: Equilibrium

63) Multiple-Object Accelerating Systems: A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the 5.0-kg box pushing it against the 3.0-kg box, and, as a result, both boxes slide along the floor. How hard do the two boxes push against each other? A) 12 N B) 20 N C) 24 N D) 32 N E) 0 N Answer: A Topic: Multiple-Object Accelerating Systems

64) --65) Friction: A bulldozer attempts to drag a log weighing 500 N along the rough horizontal ground. The cable attached to the log makes an angle of 30° above the ground. The coefficient of static friction between the log and the ground is 0.50, and the coefficient of kinetic friction is 0.35. What minimum tension is required in the cable in order for the log to begin to slide? Answer: 220 N Topic: Friction

66) Friction: A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A horizontal 140-N force is applied to the box. What is the friction force on the box? A) 140 N B) 160 N C) 16.5 N D) 0.00 N E) 42 N Answer: A Topic: Friction

67) Friction: You push downward on a trunk at an angle 25° below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move? A) 81 kg B) 93 kg

C) 73 kg D) 112 kg Answer: A Topic: Friction

68) Friction: The figure shows a system consisting of three blocks, a light frictionless pulley, and light connecting ropes that act horizontally on the upper two blocks. The 9.0-kg block is on a perfectly smooth horizontal table. The surfaces of the 12-kg block are rough, with µk = 0.30 between the 12-kg and 9.0-kg blocks. The mass M of the hanging block is set so that it descends at a constant velocity of 3.25 m/s. (a) What is the mass M of the hanging block? (b) The mass M is now changed to 5.0 kg, causing it to accelerate downward after it is released. What is the acceleration of the hanging mass?

Answer: (a) 3.6 kg (b) 0.98 m/s2 Topic: Friction

69) Slanting Surfaces With Friction: A 200-g hockey puck is launched at an initial speed of 16 m/s up a metal ramp that is inclined at a 30° angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are µs = 0.40 and µk = 0.30, respectively. What vertical height does the puck reach above its starting point? A) 8.6 cm B) 17 cm C) 13 cm D) 4.2 cm Answer: A Topic: Slanting Surfaces With Friction

70) … 71) … 72) Uniform Circular Motion: A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km. What is the magnitude of the friction force required to keep the car from sliding? A) 9000 N B) 9800 N

C) 300 N D) 900 N E) 3000 N Answer: A Topic: Uniform Circular Motion

73) Uniform Circular Motion: A 2.0-kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m. What is the magnitude of the net force on the ball? A) 0 N B) 20 N C) 40 N D) 50 N E) 100 N Answer: E Topic: Uniform Circular Motion

74) --75) Banked Curves: What is the proper banking angle for an Olympic bobsled to negotiate a 100m radius turn at 35 m/s without skidding? A) 31° B) 41° C) 51° D) 61° Answer: C Topic: Banked Curves...