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front 1 If the sum of the external forces on an object is zero, then the sum of the external torques on it must also be zero. A) True B) False | back 1 B) False |

front 2 If the sum of the external torques on an object is zero, then the sum of the external forces on it must also be zero. A) True B) False | back 2 B) False |

front 3 If the sum of both the external torques and the external forces on an object is zero, then the object must be at rest. A) True B) False | back 3 B) False |

front 4 If an object remains at rest, then the sum of both the external torques and the external forces on the object must be zero. A) True B) False | back 4 A) True |

front 5 When a car is weighed, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to A) the weight under the front wheels. B) the weight under the rear wheels. C) the average of the two weights. D) the sum of the two weights. E) the difference of the two weights. | back 5 D) the sum of the two weights. |

front 6 Tensile stress is A) the strain per unit length. B) the same as force. C) the ratio of the change in length. D) applied force per cross-sectional area. | back 6 D) applied force per cross-sectional area. |

front 7 Tensile strain is A) the ratio of the change in length to the original length. B) the stress per unit area. C) the applied force per unit area. D) the ratio of stress to elastic modulus. | back 7 A) the ratio of the change in length to the original length. |

front 8 Which one of the following is an accurate statement? A) The ratio of tensile stress to tensile strain is called Young's modulus. B) "Strain" has a meaning very close to "force." C) "Stress" has a meaning very close to "stretch." D) Tensile stress is measured in newtons. E) Tensile strain is measured in meters. | back 8 A) The ratio of tensile stress to tensile strain is called Young's modulus. |

front 9 The graph in the figure shows the tensile stress as a function of the tensile strain in a certain wire. What does the slope of this graph give us for this wire? A) the pressure in the wire B) Young's modulus for the material of the wire C) the tensile stress in the wire D) the tension in the wire E) the percent change in the length of the wire | back 9 B) Young's modulus for the material of the wire |

front 10 A large 75-kg lighting fixture can be hung from wires of identical
size and shape made of aluminum, brass, or copper. The values of
Young's modulus for these metals are 0.70 × 1011 Pa (aluminum), 0.91 ×
1011 (brass), and 1.1 × 1011 (copper). Which wire would stretch the
A) aluminum B) brass C) copper | back 10 C) copper |

front 11 A 25-kg piece of equipment can be hung by steel wires of length 1.00 m, 2.00 m, or 3.00 m. If all the wires have the same diameter, which one will stretch the greatest distance? A) the 1.00-m wire B) the 2.00-m wire C) the 3.00-m wire D) They will all stretch by the same distance. | back 11 C) the 3.00-m wire |

front 12 A 25-kg piece of equipment can be hung by steel wires of length 1.00 m, 2.00 m, or 3.00 m. If all the wires have the same diameter, which one will stretch the greatest percent? A) the 1.00-m wire B) the 2.00-m wire C) the 3.00-m wire D) They will all stretch by the same percent. | back 12 D) They will all stretch by the same percent. |

front 13 Two wires are made out of the same metal, but one wire is twice as long as the other wire. Which wire will have the greatest elastic modulus? A) the shorter wire B) the longer wire C) It will be the same for both wires. | back 13 C) It will be the same for both wires. |

front 14 Which of the following are SI units of Young's modulus? (There could be more than one correct choice.) A) N/m ∙ s2 B) kg/m2 C) kg ∙ m/s2 D) kg/m ∙ s2 E) kg ∙ m2/s2 | back 14 D) kg/m ∙ s2 |

front 15 As one stretches a metal wire, which condition is reached first? A) the elastic limit B) the breaking point C) the proportional limit | back 15 C) the proportional limit |

front 16 An ornament of mass 40.0 g is attached to a vertical ideal spring with a force constant (spring constant) of 20.0 N/m. The ornament is then lowered very slowly until the spring stops stretching. How much does the spring stretch? A) 0.00200 m B) 0.0196 m C) 0.0816 m D) 0.800 m E) 0.200 m | back 16 B) 0.0196 m |

front 17 A force of stretches a very light ideal spring from equilibrium. What is the force constant (spring constant) of the spring? A) 41 N/m B) 22 N/m C) 34 N/m D) 46 N/m | back 17 A) 41 N/m |

front 18 A very light ideal spring stretches by when it is used to hang a 135-N object. What is the weight of a piece of electronic equipment that would stretch the spring by if you hung the equipment using the spring? A) 289 N B) 63 N C) 176 N D) 405 N | back 18 A) 289 N |

front 19 An object attached to a spring is pulled across a horizontal frictionless surface. If the force constant (spring constant) of the spring is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at what is the mass of the object? A) 28 kg B) 24 kg C) 31 kg D) 36 kg | back 19 A) 28 kg |

front 20 A 3.0-kg brick rests on a perfectly smooth ramp inclined at 34° above the horizontal. The brick is kept from sliding down the plane by an ideal spring that is aligned with the surface and attached to a wall above the brick. The spring has a spring constant (force constant) of 120 N/m. By how much does the spring stretch with the brick attached? A) 360 cm B) 240 cm C) 14 cm D) 24 cm E) 36 cm | back 20 C) 14 cm |

front 21 A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the magnitude of the minimum force, applied 0.30 m on the other side of the pivot, that is needed to make the child lift off the ground? A) 75 N B) 740 N C) 23 N D) 44 N E) 66 N | back 21 B) 740 N |

front 22 A 15-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the minimum distance, on the other side of the pivot, such that a 220-N force will make the child lift off the ground? A) 1.0 m B) 1.5 m C) 0.10 m D) 9.8 m E) 2.4 m | back 22 A) 1.0 m |

front 23 An irregularly shaped object that is 10 m long is placed with each end on a scale. If the scale on the right reads while the scale on the left reads how far from the left end is the center of gravity of this object? A) 5.7 m B) 7.4 m C) 4.3 m D) 14 m | back 23 A) 5.7 m |

front 24 A uniform 1200-N piece of medical apparatus that is 3.5 m long is
suspended horizontally by two vertical wires at its ends. A small but
dense 550-N weight is placed on the apparatus 2.0 m from one end, as
shown in the figure. What are the tensions, A) B) C) D) E) | back 24 D) |

front 25 A meter stick balances at the 50.0-cm mark. If a mass of 50.0 g is placed at the 90.0-cm mark, the stick balances at the 61.3-cm mark. What is the mass of the meter stick? A) 127 g B) 178 g C) 89.7 g D) 32.6 g E) 73.4 g | back 25 A) 127 g |

front 26 A child is trying to stack two uniform bricks, each 24 cm long, so
they will protrude as far as possible over the edge of a table without
tipping over, as shown in the figure. What is the maximum possible
overhang distance A) 10 cm B) 12 cm C) 14 cm D) 16 cm E) 18 cm | back 26 E) 18 cm |

front 27 A uniform 40-N board supports two children weighing 500 N and 350 N. If the support is at the center of the board and the 500-N child is 1.5 m from its center, how far is the 350-N child from the center? A) 1.1 m B) 1.5 m C) 2.1 m D) 2.7 m | back 27 C) 2.1 m |

front 28 To determine the location of the center of mass (or center of gravity) of a car, the car is driven over a scale on a horizontal floor. When the front wheels are over the scale, the weight recorded by the scale is 5800 N, and when the rear wheels are over the scale, the scale reads 6500 N. The distance between the front and rear wheels is measured to be 3.20 m. How far behind the front wheels is the center of mass located? A) 0.845 m B) 1.50 m C) 1.59 m D) 1.69 m E) 1.72 m | back 28 D) 1.69 m |

front 29 A 120-kg refrigerator that is 2.0 m tall and 85 cm wide has its center of mass at its geometrical center. You are attempting to slide it along the floor by pushing horizontally on the side of the refrigerator. The coefficient of static friction between the floor and the refrigerator is 0.30. Depending on where you push, the refrigerator may start to tip over before it starts to slide along the floor. What is the highest distance above the floor that you can push the refrigerator so that it will not tip before it begins to slide? A) 0.71 m B) 1.0 m C) 1.2 m D) 1.4 m E) 1.6 m | back 29 D) 1.4 m |

front 30 A uniform rod weighs 40 N and is 1.0 m long. It is hinged to a wall at the left end, and held in a horizontal position at the right end by a vertical string of negligible weight, as shown in the figure. What is the magnitude of the torque due to the string about a horizontal axis that passes through the hinge and is perpendicular to the rod? The hinge is very small with negligible friction. A) 40 N ∙ m B) 10 N ∙ m C) 5.0 N ∙ m D) 20 N ∙ m E) 30 N ∙ m | back 30 D) 20 N ∙ m |

front 31 A mobile is shown in the figure. The horizontal supports have
negligible mass. Assume that all the numbers given in the figure are
accurate to two significant figures. What mass A) 18 g B) 30 g C) 36 g D) 60 g E) 90 g | back 31 C) 36 g |

front 32 An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal, as shown in the figure. His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass) is 12 cm from the elbow-joint pivot. How much force must the extensor muscle (which is M in the figure) in the upper arm exert on the lower arm? A) 100 N B) 500 N C) 1000 N D) 1500 N | back 32 C) 1000 N |

front 33 A store's sign has a mass of 20 kg and is 3.0 m long. It is uniform, so its center of gravity is at the center of the sign. It is supported horizontally by a small loose bolt attached to the wall at one end and by a wire at the other end, as shown in the figure. What is the tension in the wire? A) 460 N B) 230 N C) 120 N D) 200 N | back 33 B) 230 N |

front 34 A store's sign has a mass of 20 kg and is 3.0 m long. It is uniform,
so its center of gravity is at the center of the sign. It is supported
horizontally by a small loose bolt attached to the wall at one end and
by a wire at the other end, as shown in the figure. What is the
magnitude of the A) 460 N B) 230 N C) 200 N D) 120 N | back 34 B) 230 N |

front 35 A 40-kg uniform ladder that is 5.0 m long is placed against a smooth
wall at a height of A) 740 N B) 1300 N C) 980 N D) 900 N E) 1100 N | back 35 A) 740 N |

front 36 A 100-kg nonuniform boom that is 6.0 m long is loosely pinned at the pivot at P. A 600-kg concrete block is suspended from the end of the boom at A, as shown in the figure. The boom forms a 30° angle above the horizontal, and is supported by a 4.0-m cable between points D and B. Point B is 4.0 m from P, and point D is 4.0 m above P. The center of mass of the boom is at point C, which is 2.0 m from P. Assume that all the quantities shown in the figure are accurate to two significant figures. What is the tension in the cable connected between points B and D? A) 9300 N B) 8400 N C) 8100 N D) 7500 N E) 6900 N | back 36 A) 9300 N |

front 37 ) In the figure, a uniform ladder of weight 200 N and length 10 m
leans against a perfectly smooth wall. A firefighter of weight 600 N
climbs a distance A) 3.9 m B) 5.0 m C) 6.0 m D) 6.3 m E) 8.4 m | back 37 D) 6.3 m |

front 38 A 3.00-m-long ladder, weighing 200 N, leans against a smooth vertical wall with its base on a horizontal rough floor, a distance of 1.00 m away from the wall. The ladder is not completely uniform, so its center of gravity is 1.20 m from its base. What force of friction must the floor exert on the base of the ladder to prevent the ladder from sliding down? A) 93.3 N B) 130 N C) 28.3 N D) 102 N E) 150 N | back 38 C) 28.3 N |

front 39 A 5.00-m-long uniform ladder, weighing 200 N, rests against a smooth vertical wall with its base on a horizontal rough floor, a distance of 1.20 m away from the wall. The coefficient of static friction between the ladder and the floor is 0.200. How far up the ladder, measured along the ladder, can a 600-N person climb before the ladder begins to slip? A) 1.50 m B) 1.26 m C) 1.05 m D) 3.95 m E) 4.56 m | back 39 E) 4.56 m |

front 40 A stepladder consists of two halves that are hinged at the top and
connected by a tie rod which keeps the two halves from spreading
apart. In this particular instance, the two halves are 2.5 m long, the
tie rod is connected to the center of each half and is 70 cm long. An
800-N person stands 3/5 of the way up the stepladder, as shown in the
figure. The ladder is light enough that we can neglect its weight, and
it rests on an extremely smooth floor. What is the tension in the tie
rod? ( A) 140 N B) 240 N C) 280 N D) 360 N E) 560 N | back 40 A) 140 N |

front 41 A 320-g ball and a 400-g ball are attached to the two ends of a string that goes over a pulley with a radius of 8.7 cm. Because of friction in its axle, the pulley does not begin to rotate. What is the magnitude of the frictional torque at the axle of the pulley if the system remains at rest when the balls are released? A) 0.068 N ∙ m B) 0.61 N ∙ m C) 0.079 N ∙ m D) 0.063 N ∙ m E) 0.00070 N ∙ m | back 41 A) 0.068 N ∙ m |

front 42 A steel wire, 3.2 m long, has a diameter of 1.2 mm. The wire
stretches 1.6 mm when it bears a load. Young's modulus for steel is
2.0 A) 12 kg. B) 16 kg. C) 20 kg. D) 24 kg. E) 28 kg. | back 42 A) 12 kg. |

front 43 When a 125-kg piece of equipment is hung from a steel wire of diameter 6.00 mm, it stretches the wire by 4.00 mm. If instead the wire had a diameter of 3.00 mm, but all else were the same, by what distance would the same equipment stretch the wire? A) 16.0 mm B) 8.00 mm C) 4.00 mm D) 2.00 mm E) 1.00 mm | back 43 A) 16.0 mm |

front 44 When a 125-kg piece of equipment is hung from a steel wire of length 75 cm, it stretches the wire by 4.00 mm. If instead the wire had a length of 150 cm, but all else were the same, by what distance would the same equipment stretch the wire? A) 16.0 mm B) 8.00 mm C) 4.00 mm D) 2.00 mm E) 1.00 mm | back 44 B) 8.00 mm |

front 45 A cable is 100-m long and has a cross-sectional area of 1.0 mm2. A 1000-N force is applied to stretch the cable. Young's modulus for the cable is 1.0 × 1011 N/m2. How far does the cable stretch? A) 0.010 m B) 0.10 m C) 1.0 m D) 10 m | back 45 C) 1.0 m |

front 46 A solid steel column is 4.0 m long and 0.20 m in diameter. Young's modulus for this steel is 2.0 × 1011 N/m2. By what distance does the column shrink when a 5000-kg truck is supported by it? A) 8.0 × 10-7m B) 3.2 × 10-6m C) 7.8 × 10-6m D) 3.1 × 10-5m | back 46 D) 3.1 × 10-5m |

front 47 A wire of diameter 0.20 mm stretches by 0.20% when a 6.28-N force is applied to it. What is Young's modulus for this wire? A) 2.5 × 1010Pa B) 1.0 × 1011Pa C) 2.5 × 1012Pa | back 47 B) 1.0 × 1011Pa |

front 48 A 50-kg load is suspended from a steel wire of diameter 1.0 mm and length 11.2 m. By what distance will the wire stretch? Young's modulus for steel is 2.0 × 1011 Pa. A) 1.5 cm B) 2.5 cm C) 3.5 cm D) 4.5 cm | back 48 C) 3.5 cm |

front 49 A bridge piling has a cross-sectional area of 1.250 m2 and supports a load of 1875 N. What is the stress on the column? A) 1875 N B) 1875 N/m2 C) 1500 N/m2 D) 2344 N/m2 | back 49 C) 1500 N/m2 |

front 50 An aluminum wire 2.0 m long and 2.0 mm in diameter supports a 10.0-kg fixture. What is the stress in the wire? Young's modulus for aluminum is 7.0 × 1010 N/m2. A) 3.1 × 107N/m2 B) 6.2 × 107N/m2 C) 9.3 × 107N/m2 D) 1.2 × 108N/m2 | back 50 A) 3.1 × 107N/m2 |

front 51 A brass wire 2.0 m long and 2.0 mm in diameter supports a 10.0-kg fixture. By what distance did this fixture stretch the wire? Young's modulus for brass is 10 × 1010 N/m2. A) 0.11 mm B) 0.22 mm C) 0.33 mm D) 0.62 mm | back 51 D) 0.62 mm |

front 52 A vertical 30-cm steel rod, 1.0 cm in diameter, supports a 300-kg mass. What is the change in length of the rod caused by this mass? Young's modulus for steel is 2.0 × 1011 N/m2. A) 5.6 × 10-5m B) 6.5 × 10-5m C) 5.6 × 10-6m D) 6.5 × 10-6m E) 6.5 × 10-4m | back 52 A) 5.6 × 10-5m |

front 53 A 50-kg air conditioner is placed on top of a concrete pad that is 20 cm thick and has a cross-sectional area of 3.0 m2. What is the change in thickness of the pad caused by the air conditioner? Young's modulus for concrete is 2.3 × 1010 N/m2. A) 1.4 × 10-9m B) 2.8 × 10-9m C) 1.4 × 10-8m D) 1.4 × 10-7m E) 2.8 × 10-8m | back 53 A) 1.4 × 10-9m |

front 54 A 1200-kg car is being raised at a constant speed if 25 cm/s by a crane, using a 20-m long steel cable that is 1.5 cm in diameter. Young's modulus for steel is 2.0 × 1011 Pa. What is the change in length of the cable caused by the car? A) 6.7 mm B) 6.7 cm C) 3.3 mm D) 3.3 cm E) 3.3 m | back 54 A) 6.7 mm |

front 55 A 1200-kg car is being raised with a constant acceleration of 2.53 m/s2 by a crane, using a 20-m long steel cable that is 1.5 cm in diameter. Young's modulus for steel is 2.0 × 1011 N/m2. What is the change in length of the cable caused by lifting the car? A) 8.4 mm B) 8.4 cm C) 4.9 mm D) 4.9 cm E) 4.9 m | back 55 A) 8.4 mm |

front 56 A piano wire has a radius of 0.50 mm. One end is fixed and the other is wrapped around a tuning peg, which has a diameter of 3.5 mm and is 80 cm away. After the wire just becomes taut, the peg is given three full turns. What is the tension in the wire? Young's modulus for steel is 2.0 × 1011 N/m2. A) 3.8 kN B) 4.3 kN C) 6.5 kN D) 8.7 kN E) 9.8 kN | back 56 C) 6.5 kN |