PHYS 1511 TA Sample Questions For Exam I

7. Using the dimensions given for the variables in the table, determine which one of the following expressions is correct. variable dimension f 1 [T] l [L] g 2 [L] [T] A) 2 g f l   B) f = 2  gl C) 2 g f l   D) 2 l f g   E) 2 f gl   Ans: C

14. A physics text has 544 sheets (1088 pages) and is 34.3 millimeters thick between the inside front cover and the inside back cover. What is the thickness of a single sheet? A) 6.36 × 10 –4 m B) 3.16 × 10 –2 m C) 6.28 × 10 –3 m D) 7.24 × 10 –6 m E) 6.31 × 10 –5 m Ans: E 15. A displacement vector has a magnitude of 810 m and points at an angle of 18° above the positive x axis. What are the x and y scalar components of this vector? x scalar component y scalar component A) 770 m 250 m B) 560 m 585 m C) 585 m 560 m D) 250 m 750 m E) 713 m 385 m Ans: A 16. A particle travels along a curved path between two points P and Q as shown. The displacement of the particle does not depend on A) the location of P. B) the location of Q. C) the distance traveled from P to Q. D) the shortest distance between P and Q. E) the direction of Q from P. Ans: C

22. A bus leaves New York City, takes a non-direct route and arrives in St. Louis, Missouri 23 hours, 16 minutes later. If the distance between the two cities is 1250 km, what is the magnitude of the bus' average velocity? A) 37.2 km/h B) 41.4 km/h C) 46.0 km/h D) 53.7 km/h E) 58.1 km/h Ans: D 23. Alexa's hair grows with an average speed of 3.5 × 10 –9 m/s. How long does it take her hair to grow 0.30 m? Note: 1 yr = 3.156 × 10 7 s. A) 1.9 yr B) 1.3 yr C) 0.37 yr D) 5.4 yr E) 2.7 yr Ans: E 24 . Carl Lewis set a world record for the 100.0-m run with a time of 9.86 s. If, after reaching the finish line, Mr. Lewis walked directly back to his starting point in 90.9 s, what is the magnitude of his average velocity for the 200.0 m? A) 0 m/s B) 1.10 m/s C) 1.98 m/s D) 5.60 m/s E) 10.1 m/s Ans: A 25. What is the average speed of the car for one complete lap? A) r t B) 2 r t C) r t  D) 2 r t  E) zero meters/second Ans: D 26. A car is moving at a constant velocity when it is involved in a collision. The car comes to

A) 0.6 s B) 1.0 s C) 1.2 s D) 1.4 s E) 2.0 s Ans: B 35. A ball is dropped from rest from a tower and strikes the ground 110 m below. Approximately how many seconds does it take the ball to strike the ground after being dropped? Neglect air resistance. A) 2.50 s B) 3.50 s C) 4,74 s D) 12.5 s E) 16.0 s Ans: C 36. Ryan throws a tennis ball vertically upward. The ball returns to the point of release after 3.5 s. What is the speed of the ball as it is released? A) 0 m/s B) 14 m/s C) 17 m/s D) 21 m/s E) 34 m/s Ans: C 37. A rock is dropped from rest from a height h above the ground. It falls and hits the ground with a speed of 11 m/s. From what height should the rock be dropped so that its speed on hitting the ground is 22 m/s? Neglect air resistance. A) 1.4 h B) 2.0 h C) 3.0 h D) 4.0 h E) 0.71 h Ans: D

A rock, dropped from rest near the surface of an atmosphere-free planet, attains a speed of 20.0 m/s after falling 8.0 meters. 42. What is the magnitude of the acceleration due to gravity on the surface of this planet? A) 0.40 m/s 2 B) 1.3 m/s 2 C) 2.5 m/s 2 D) 25 m/s 2 E) 160 m/s 2 Ans: D 43. A park ranger wanted to measure the height of a tall tree. The ranger stood 9.50 m from the base of the tree; and he observed that his line of sight made an angle of 65.2° above the horizontal as he looked at the top of the tree. The park ranger's eyes are 1.80 m above the ground. What is the height of the tree? A) 5.84 m B) 8.77 m C) 11.7 m D) 17.3 m E) 22.4 m Ans: E 44. A delivery truck leaves a warehouse and travels 2.60 km north. The truck makes a left turn and travels 1.25 km west before making a right turn to travel 1.40 km north to arrive at its destination. What is the magnitude and direction of the truck's displacement from the warehouse? A) 4.00 km, 18.2° north of west B) 5.25 km, 59.8° north of west C) 6.33 km, 70.2° north of west D) 3.40 km, 55.0° north of west E) 4.19 km, 72.6° north of west Ans: E 45. A car travels due east at 22 m/s. It makes a turn due south and continues to travel at 22 m/s. What is the change in velocity of the car? A) 22 m/s, due east B) 22 m/s, due south C) 31 m/s, 45° south of west D) 31 m/s, 45° south of east E) zero m/s Ans: C

A shell is fired with a horizontal velocity in the positive x direction from the top of an 80-m high cliff. The shell strikes the ground 1330 m from the base of the cliff. The drawing is not to scale. 54. Determine the initial speed of the shell. A) 4.0 m/s B) 9.8 m/s C) 82 m/s D) 170 m/s E) 330 m/s Ans: E 55. A basketball is launched with an initial speed of 8.0 m/s and follows the trajectory shown. The ball enters the basket 0.96 s after it is launched. What are the distances x and y ? Note : The drawing is not to scale. x y A) 5.4 m 0.73 m B) 7.7 m 0.91 m C) 5.4 m 0.91 m D) 5.7 m 0.73 m E) 5.4 m 5.4 m Ans: C

63. Which one of the following terms is used to indicate the natural tendency of an object to remain at rest or in motion at a constant speed along a straight line? A) velocity B) inertia C) acceleration D) equilibrium E) force Ans: B 64. A net force F  is required to give an object with mass m an acceleration a . If a net force 6 F  is applied to an object with mass 2 m , what is the acceleration on this object? A) a  B) 2 a  C) 3 a  D) 4 a  E) 6 a  Ans: C 65. The figure shows the velocity versus time curve for a car traveling along a straight line. Which of the following statements is false? A) No net force acts on the car during interval B . B) Net forces act on the car during intervals A and C . C) Opposing forces may be acting on the car during interval B . D) Opposing forces may be acting on the car during interval C . E) The magnitude of the net force acting during interval A is less than that during C . Ans: E

66. A net force of 25 N is applied for 5.7 s to a 12-kg box initially at rest. What is the speed of the box at the end of the 5.7-s interval? A) 1.8 m/s B) 12 m/s C) 3.0 m/s D) 7.5 m/s E) 30 m/s Ans: B 67. A 975-kg car accelerates from rest to 26.7 m/s in a distance of 120 m. What is the magnitude of the average net force acting on the car? A) 740 N B) 2900 N C) 91 N D) 1300 N E) 7900 N Ans: B 68. Two forces act on a 16-kg object. The first force has a magnitude of 68 N and is directed 24° north of east. The second force is 32 N, 48° north of west. What is the acceleration of the object resulting from the application of these two forces to the object? A) 1.6 m/s 2 , 5.5° north of east B) 1.9 m/s 2 , 18° north of west C) 2.4 m/s 2 , 34° north of east D) 3.6 m/s 2 , 5.5° north of west E) 4.1 m/s 2 , 52° north of east Ans: E 69. An apple crate with a weight of 225 N accelerates along a frictionless surface as the crate is pulled with a force of 14.5 N as shown in the drawing. What is the horizontal acceleration of the crate? A) 1.40 m/s 2 B) 0.427 m/s 2 C) 1.29 m/s 2 D) 0.597 m/s 2 E) 0.644 m/s 2 Ans: D

70. Two forces act on a 4.5-kg block resting on a frictionless surface as shown. What is the magnitude of the horizontal acceleration of the block? A) 1.8 m/s 2 B) 1.2 m/s 2 C) 0.82 m/s 2 D) 3.2 m/s 2 E) 8.9 m/s 2 Ans: A A 70.0-kg astronaut pushes to the left on a spacecraft with a force F  in “gravity-free” space. The spacecraft has a total mass of 1.0 × 10 4 kg. During the push, the astronaut accelerates to the right with an acceleration of 0.36 m/s 2 . 71. Which one of the following statements concerning this situation is true? A) The spacecraft does not move, but the astronaut moves to the right with a constant speed. B) The astronaut stops moving after he stops pushing on the spacecraft. C) The force exerted on the astronaut is larger than the force exerted on the spacecraft. D) The force exerted on the spacecraft is larger than the force exerted on the astronaut. E) The velocity of the astronaut increases while he is pushing on the spacecraft. Ans: E 72. Determine the magnitude of the acceleration of the spacecraft. A) 51.4 m/s 2 B) 0.36 m/s 2 C) 2.5 × 10 –3 m/s 2 D) 7.0 × 10 –3 m/s 2 E) 3.97 × 10 –4 m/s 2 Ans: C

73. Two point masses m and M are separated by a distance d . If the distance between the masses is increased to 3 d , how does the gravitational force between them change? A) The force will be one-third as great. B) The force will be one-ninth as great. C) The force will be three times as great. D) The force will be nine times as great. E) It is impossible to determine without knowing the numerical values of m , M , and d . Ans: B 74. Two point masses m and M are separated by a distance d . If the separation d remains fixed and the masses are increased to the values 3 m and 3 M respectively, how does the gravitational force between them change? A) The force will be one-third as great. B) The force will be one-ninth as great. C) The force will be three times as great. D) The force will be nine times as great. E) It is impossible to determine without knowing the numerical values of m , M , and d . Ans: D 75. What is the weight of a 2.50-kg bag of sand on the surface of the earth? A) 2.50 N B) 9.80 N C) 24.5 N D) 49.0 N E) 98.0 N Ans: C 76. What is the magnitude of the gravitational force acting on a 79.5-kg student due to a 58.0-kg student sitting 2.40 m away in the classroom? A) 3.14 × 10 –9 N B) 5.33 × 10 –8 N C) 7.91 × 10 –10 N D) 1.41 × 10 –7 N E) 6.29 × 10 –8 N Ans: B

77. A 44-kg child steps onto a scale and the scale reads 430 N. What is the magnitude of the normal force acting on the child? A) 44 N B) 215 N C) 430 N D) 645 N E) 860 N Ans: C A force P  pulls on a crate of mass m that is in contact with a rough surface. The figure shows the magnitudes and directions of the forces that act on the crate in this situation. W  represents the weight of the crate. N F  represents the normal force on the crate, and f  represents the frictional force. 78. Which statement best describes the motion of the crate? A) The crate must be at rest. B) The crate must be moving with constant velocity. C) The crate must be moving with constant acceleration. D) The crate may be either at rest or moving with constant velocity. E) The crate may be either at rest or moving with constant acceleration. Ans: D

79. Note the following situations: In which case will the magnitude of the normal force on the block be equal to ( Mg + F sin  )? A) case 1 only B) case 2 only C) both cases 1 and 2 D) both cases 2 and 3 E) cases 1, 2, and 3 Ans: A A block is pulled along a rough level surface at constant speed by the force P  . The figure shows the free-body diagram for the block. N F  represents the normal force on the block; and f  represents the force of kinetic friction. 80. What is the magnitude of N F  ? A) 2 mg B) P C) f D) mg E) This cannot be determined from the information given. Ans: D

81. Two identical blocks are pulled along a rough surface as suggested in the figure. Which one of the following statements is false ? A) The coefficient of kinetic friction is the same in each case. B) A force of the same magnitude is needed to keep each block moving. C) A force of the same magnitude was required to start each block moving. D) The normal force exerted on the blocks by the surface is the same for both blocks. E) The magnitude of the force of kinetic friction is greater for the block on the right. Ans: E 82. A crate rests on the flatbed of a truck that is initially traveling at 15 m/s on a level road. The driver applies the brakes and the truck is brought to a halt in a distance of 38 m. If the deceleration of the truck is constant, what is the minimum coefficient of friction between the crate and the truck that is required to keep the crate from sliding? A) 0.20 B) 0.30 C) 0.39 D) 0.59 E) This cannot be determined without knowing the mass of the crate. Ans: B

83. In an experiment with a block of wood on an inclined plane, with dimensions shown in the figure, the following observations are made: (1) If the block is placed on the inclined plane, it remains there at rest. (2) If the block is given a small push, it will accelerate toward the bottom of the incline without any further pushing. Which one of the following statements is the best conclusion that can be drawn from these observations? A) The coefficient of kinetic friction must be negative. B) Both coefficients of friction must be less than 0.25. C) Both coefficients of friction must be greater than 0.25. D) The coefficient of static friction must be less than the coefficient of kinetic friction. E) The coefficient of static friction is greater than 0.25 while the coefficient of kinetic friction is less than 0.25. Ans: E 84. In a tug-of-war, each man on a 5-man team pulls with an average force of 500 N. What is the tension in the center of the rope? A) zero newtons B) 100 N C) 500 N D) 2500 N E) 5000 N Ans: E

85. A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure. Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be A) less than zero. B) greater than 2. C) greater than 1, but less than 2. D) greater than 0.5, but less than 1. E) less than 0.5, but greater than or equal to zero. Ans: E A block of mass M is held motionless on a frictionless inclined plane by means of a string attached to a vertical wall as shown in the drawing. 86. What is the magnitude of the tension in the string? A) zero newtons B) Mg C) Mg cos  D) Mg sin  E) Mg tan  Ans: D 87. If the string breaks, what is the magnitude of the acceleration of the block as it slides down the inclined plane? A) zero m/s 2 B) g C) g cos  D) g sin  E) g tan  Ans: D 88. Assume the plane is not frictionless and the string breaks, what minimum value of the

coefficient of static friction,  s , would prevent the block from sliding down the inclined plane? A) zero B) 1 C) cos  D) sin  E) tan  Ans: E A system of two cables supports a 150-N ball as shown. 89. What is the tension in the right-hand cable? A) 87 N B) 150 N C) 170 N D) 260 N E) 300 N Ans: E A block is at rest on a rough inclined plane and is connected to an object with the same mass as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coefficient of static friction between the block and the plane is µ s ; and the coefficient of kinetic friction is  k . 90. What is the magnitude of the static frictional force acting on the block? A) mg sin  B) mg cos  C) mg (1 – sin  ) D) mg (1 – cos  ) E) mg Ans: C 91. If the rope were cut between the block and the pulley, what would be the magnitude of the

acceleration of the block down the plane? A) g B) g –  k sin  C) g –  k cos  D) g (tan  –  k sin  ) E) g (sin  –  k cos  ) Ans: E 92. If the mass of the suspended object is doubled, what will be the acceleration of the block up the plane? A) g (2 –  k sin  ) B) 2 g (  k sin  – cos  ) C) g (2tan  –  k sin  ) D) g (2 – sin  –  k cos  ) E) g (2cos  –  k sin  ) Ans: D 93. A ball moves with a constant speed of 4 m/s around a circle of radius 0.25 m. What is the period of the motion? [Hint: For this calculation, you need to know the circumference of the circle.] A) 0.1 s B) 0.4 s C) 0.7 s D) 1 s E) 2 s Ans: B 94. The second hand on a watch has a length of 4.50 mm and makes one revolution in 60.00 s. What is the speed of the end of the second hand as it moves in uniform circular motion? A) 9.42 × 10 –4 m/s B) 2.67 × 10 –3 m/s C) 5.34 × 10 –3 m/s D) 4.71 × 10 –4 m/s E) 2.36 × 10 –5 m/s Ans: D

95. A solar-powered car is traveling at constant speed around a circular track. What happens to the centripetal acceleration of the car if the speed is doubled? A) The centripetal acceleration remains the same. B) The centripetal acceleration increases by a factor of 2. C) The centripetal acceleration increases by a factor of 4. D) The centripetal acceleration is decreased by a factor of one-half. E) The centripetal acceleration is decreased by a factor of one-fourth. Ans: C 96. A ball is whirled on the end of a string in a horizontal circle of radius R at constant speed v . Complete the following statement: The centripetal acceleration of the ball can be increased by a factor of 4 by A) keeping the speed fixed and increasing the radius by a factor of 4. B) keeping the radius fixed and increasing the speed by a factor of 4. C) keeping the radius fixed and increasing the period by a factor of 4. D) keeping the radius fixed and decreasing the period by a factor of 4. E) keeping the speed fixed and decreasing the radius by a factor of 4. Ans: E 97. A car traveling at 20 m/s follows a curve in the road so that its centripetal acceleration is 5 m/s 2 . What is the radius of the curve? A) 4 m B) 8 m C) 80 m D) 160 m E) 640 m Ans: C 98. A 0.25-kg ball attached to a string is rotating in a horizontal circle of radius 0.5 m. If the ball revolves twice every second, what is the tension in the string? A) 2 N B) 5 N C) 7 N D) 10 N E) 20 N Ans: E

99. In an amusement park ride, a child stands against the wall of a cylindrical room that is then made to rotate. The floor drops downward and the child remains pinned against the wall. If the radius of the room is 2.15 m and the relevant coefficient of friction between the child and the wall is 0.600, with what minimum speed is the child moving if he is to remain pinned against the wall? A) 7.26 m/s B) 3.93 m/s C) 12.1 m/s D) 5.93 m/s E) 9.80 m/s Ans: D 100. Complete the following statement: The maximum speed at which a car can safely negotiate a frictionless banked curve depends on all of the following except A) the mass of the car. B) the angle of banking. C) the diameter of the curve. D) the radius of the curve. E) the acceleration due to gravity. Ans: A 101. Determine the minimum angle at which a roadbed should be banked so that a car traveling at 20.0 m/s can safely negotiate the curve if the radius of the curve is 2.00 × 10 2 m. A) 0.200° B) 0.581° C) 11.5° D) 19.6° E) 78.2° Ans: C 102. The Earth exerts the necessary centripetal force on an orbiting satellite to keep it moving in a circle at constant speed. Which one of the following statements best explains why the speed of the satellite does not change although there is a net force exerted on it? A) The satellite is in equilibrium. B) The acceleration of the satellite is zero m/s 2 . C) The centripetal force has magnitude mv 2 / r . D) The centripetal force is canceled by the reaction force. E) The centripetal force is always perpendicular to the velocity. Ans: E

103 . An object weighs 10 N on the earth's surface. What is the weight of the object on a planet that has one tenth the earth's mass and one half the earth's radius? A) 4 N B) 2 N C) 1 N D) 10 N E) 20 N Ans: A A 2400-kg satellite is in a circular orbit around a planet. The satellite travels with a constant speed of 6670 m/s. The radius of the circular orbit is 8.92 × 10 6 m. 104. At the instant shown in the figure, which arrow indicates the direction of the net force on the satellite? A) (a) B) (b) C) (c) D) (d) E) (e) Ans: A

105. A space station is designed in the shape of a large, hollow donut that is uniformly rotating. The outer radius of the station is 350 m. With what period must the station rotate so that a person sitting on the outer wall experiences “artificial gravity,” i.e. an acceleration of 9.8 m/s 2 ? A) 230 s B) 170 s C) 110 s D) 76 s E) 38 s Ans: E 106. A plane is traveling at 200 m/s following the arc of a vertical circle of radius R . At the top of its path, the passengers experience “weightlessness.” To one significant figure, what is the value of R ? A) 200 m B) 1000 m C) 2000 m D) 4000 m E) 40 000 m Ans: D