ASVAB Practice

Mechanical Comprehension

200 Mechanical Comprehension practice questions, each with the correct answer and the method behind it.

Practice tests Practice test 1 Practice test 2 Practice test 3 Practice test 4 Practice test 5 Practice test 6 Practice test 7 Practice test 8
  1. The difference between an object's mass and its weight is that weightis the force gravity exerts on that mass
  2. Which statement matches the first of Newton's laws of motion?keeps doing what it is doing until a force acts on it
  3. What force is needed to accelerate a 10 kilogram object at 3 metres per second squared?30 newtons
  4. What is the momentum of a 4 kilogram object moving at 5 metres per second?20 kilogram-metres per second
  5. Ignoring air resistance, a heavy ball and a light ball dropped together from the same height willreach the ground at the same moment
  6. Two forces act on a crate along the same line: 30 newtons to the right and 20 newtons to the left. What is the net force?10 newtons to the right
  7. An object is said to be in equilibrium whenall the forces on it cancel out
  8. How much work is done pushing a crate 4 metres with a force of 50 newtons?200 joules
  9. A worker holds a heavy box perfectly still at chest height for two minutes. In the physics sense, the work done on the box iszero, because the box does not move
  10. The gravitational potential energy of a raised object depends onits mass, the pull of gravity, and its height
  11. An object possesses kinetic energy on account of itsmotion
  12. A machine does 600 joules of work in 3 seconds. What is its power output?200 watts
  13. No real machine reaches 100 percent efficiency becausesome input energy is always lost to friction and heat
  14. In a first-class lever, the fulcrum sitsbetween the effort and the load
  15. A lever has an effort arm of 8 feet and a resistance arm of 2 feet. What is its mechanical advantage?4
  16. A wheelbarrow is an example of which class of lever?Second class
  17. A 60 pound weight sits 2 feet from a fulcrum. What downward force applied 6 feet from the fulcrum on the other side will balance it?20 pounds
  18. Moving a lever's fulcrum closer to the load willincrease the mechanical advantage
  19. A pair of tweezers is an example of which class of lever?Third class
  20. A single fixed pulley provides a mechanical advantage of1
  21. In a pulley system, four rope sections support the movable block. What is the mechanical advantage?4
  22. Compared with lifting a load directly, a single movable pulley lets youuse half the force but pull twice the rope
  23. The purpose of a block and tackle is tomultiply the force applied to a load
  24. A pulley system with a mechanical advantage of 3 is used to lift 150 pounds. What effort is required, ignoring friction?50 pounds
  25. A 20-tooth gear drives a 60-tooth gear. The larger gear turnsone third as fast as the driver
  26. Two gears meshed directly together turnin opposite directions
  27. An idler gear placed between a driver and a driven gearreverses the output direction without changing the ratio
  28. When a small gear drives a much larger one, the output hasmore torque and less speed
  29. A 12-tooth gear turning at 60 revolutions per minute drives a 24-tooth gear. How fast does the larger gear turn?30 revolutions per minute
  30. A worm gear drive is chosen mainly because itgives a large speed reduction and usually cannot be driven backwards
  31. A belt running between two pulleys in a crossed figure-eight makes them turnin opposite directions
  32. An inclined plane makes a load easier to raise because itreduces the force needed, spread over a longer distance
  33. A wedge is best described asan inclined plane that moves
  34. A screw is best understood asan inclined plane wrapped around a cylinder
  35. A wheel and axle has a wheel radius of 12 inches and an axle radius of 3 inches. What is its mechanical advantage?4
  36. A loading ramp is 15 feet long and rises 3 feet. What is its mechanical advantage?5
  37. Under Pascal's principle, pressure applied to a fluid held in a closed systemis transmitted equally throughout the fluid
  38. In a hydraulic press the small piston has an area of 2 square inches and the large one 10 square inches. A force of 50 pounds on the small piston produces what force at the large one?250 pounds
  39. An object placed in water will float ifit displaces a weight of water equal to its own
  40. Water flowing through a pipe that narrows willspeed up as it passes through the narrow section
  41. A check valve in a fluid systempermits flow in one direction only
  42. Hydraulic systems use liquid rather than air because liquidsbarely compress, so motion transfers precisely
  43. A vertical column holding up a roof is primarily undercompression
  44. A cable supporting a hanging load is undertension
  45. Triangles are used throughout trusses and bracing because a trianglecannot change shape unless a side changes length
  46. A beam supported at both ends carries a load at its centre. The bending stress is greatestat the middle of the beam
  47. Compared with the friction of an object already sliding, the friction that must be overcome to start it moving is usuallygreater
  48. Bearings reduce friction in a shaft byreplacing sliding contact with rolling contact
  49. A force of 30 pounds is applied 2 feet from a pivot. How much torque does it produce?60 pound-feet
  50. Lubrication reduces friction between two surfaces byholding them apart with a film of fluid
  51. Acceleration is defined as the rate at whichvelocity changes
  52. A crate weighing 100 pounds on Earth is taken to the Moon. On the Moon it will havethe same mass but less weight
  53. A force of 20 newtons acts on a 5 kilogram mass. What acceleration results?4 metres per second squared
  54. Two forces act on a point at right angles: 8 newtons north and 6 newtons east. What is the resultant force?10 newtons
  55. Newton's second law of motion connectsforce, mass, and acceleration
  56. Seat belts matter in a sudden stop becausethe occupant's body keeps moving forward after the car halts
  57. A book lies still on a table. The forces acting on it areits weight downward and the table pushing up, equal in size
  58. How much work is done raising a 200 pound load 5 feet?1000 foot-pounds
  59. One horsepower is defined as550 foot-pounds of work per second
  60. A swinging pendulum at the very top of its arc hasmaximum potential energy and minimum kinetic energy
  61. A machine that is 80 percent efficient delivers 400 joules of useful output. How much energy went in?500 joules
  62. As a rock falls from a cliff, its energy is converted frompotential to kinetic
  63. If a vehicle's speed doubles, its kinetic energy becomesfour times as great
  64. A crowbar used to pry a nail out of a board acts as a lever of which class?First class
  65. A nutcracker is an example of which class of lever?Second class
  66. A lever has an effort arm of 10 inches and a resistance arm of 2 inches. What effort will lift a 200 pound load?40 pounds
  67. A lever with a mechanical advantage of less than one is useful because ittrades force away in exchange for speed and range of movement
  68. Sweeping with a broom, holding the top hand still and driving with the lower hand, makes the broom a lever of which class?Third class
  69. An 80 pound child sits 4 feet from the centre of a seesaw. How far from the centre must a 64 pound child sit to balance it?5 feet
  70. A pulley system with a mechanical advantage of 4 raises a load 3 feet. How much rope must be pulled through?12 feet
  71. Adding a second movable pulley to a lifting system willincrease the mechanical advantage
  72. The chief benefit of a single fixed pulley is that itchanges the direction in which the effort is applied
  73. Six rope sections support the load in a block and tackle. What effort lifts 600 pounds, ignoring friction?100 pounds
  74. In a real pulley system, the effort actually needed isa little more than the ideal calculation predicts
  75. A bevel gear is used totransmit motion between shafts that meet at an angle
  76. A rack and pinion arrangement convertsrotary motion into straight-line motion
  77. In a train of three meshed gears, the first and the last turnin the same direction
  78. Compared with a belt drive, a chain drivedoes not slip, so the ratio stays exact
  79. A 40-tooth gear meshes with a 10-tooth gear. For each full turn of the large gear, the small one turns4 times
  80. A gearbox gives a 5 to 1 reduction. With 100 pound-feet of input torque, the output torque is about500 pound-feet
  81. A large pulley drives a small pulley by belt. The small pulley turnsfaster than the large one
  82. A screw with finer threads, meaning more turns per inch, providesgreater mechanical advantage but slower travel
  83. A doorknob is an example of which simple machine?A wheel and axle
  84. A knife blade works as which simple machine?A wedge
  85. A ramp 20 feet long rises 4 feet. Ignoring friction, what force is needed to push a 500 pound load up it?100 pounds
  86. Compared with a short ramp reaching the same height, a longer ramp requiresless force applied over a greater distance
  87. A force of 200 pounds presses on a piston with an area of 8 square inches. What is the pressure?25 pounds per square inch
  88. In a hydraulic jack, the small piston compared with the large one must movea greater distance
  89. Atmospheric pressure at sea level is approximately15 pounds per square inch
  90. The water pressure at a point inside a tank depends chiefly onthe depth below the surface
  91. An air compressor stores energy bysqueezing air into a tank at high pressure
  92. A ship built of steel floats becauseits hull shape displaces more water than the ship weighs
  93. Shear stress is the kind of force that tends to make parts of a materialslide past one another
  94. The elasticity of a material describes its ability toreturn to its original shape after being deformed
  95. A beam rests on two supports and a load is placed close to one end. That support will carrymore of the load than the far support
  96. A brittle material is one thatbreaks suddenly with little bending first
  97. An object moving in a circle is held on its path by a force directedtoward the centre of the circle
  98. Hooke's law states that the distance a spring stretches isproportional to the force applied to it
  99. Placing a heavier load on a sliding object increases the friction becausethe surfaces are pressed together more firmly
  100. A mechanic needs 90 pound-feet of torque. Using a wrench 3 feet long, what force must be applied at the end?30 pounds
  101. A crate has a mass of 20 kilograms. What is its weight on Earth, using 10 m/s^2 for gravity?200 newtons
  102. An astronaut's mass is 80 kilograms on Earth. What is her mass on the Moon?80 kilograms
  103. Which of Newton's laws best explains why a passenger's body keeps moving forward when the car halts abruptly?the first law, inertia
  104. A rocket expels exhaust gas downward and rises upward. This best illustratesNewton's third law
  105. A 5 kilogram block accelerates at 4 metres per second squared. How much net force is acting on it?20 newtons
  106. A net force of 60 newtons accelerates a cart at 3 metres per second squared. What is the cart's mass?20 kilograms
  107. A 2 kilogram ball moving at 6 metres per second has how much momentum?12 kilogram-metres per second
  108. Two identical carts collide head-on at equal speeds and stick together. What happens to their combined momentum after the collision?it is zero, since the momenta cancel
  109. A ball dropped from a cliff, ignoring air resistance, gains speed at a rate of about9.8 metres per second every second
  110. A hammer and a feather are dropped together on the Moon, where there is no air. Which hits the ground first?they land at the same time
  111. A picture frame hangs motionless from a single nail. What can be said about the forces acting on it?they are balanced, summing to zero
  112. A sign is held up by two ropes pulling upward at equal angles. If one rope suddenly goes slack, what happens to the sign?it swings and drops toward the side of the slack rope
  113. A boat's engine pushes it east with 300 newtons while a current pushes it north with 400 newtons. What is the magnitude of the resultant force?500 newtons
  114. Two workers pull on a rope in exactly opposite directions with 150 newtons each. What is the net force on the rope?0 newtons
  115. How much work is done pushing a crate 8 metres across a floor with a steady force of 25 newtons?200 joules
  116. A mover applies 500 newtons to a piano but the piano does not move at all. How much work is done on the piano?0 joules
  117. A 4 kilogram object moving at 5 metres per second has how much kinetic energy?50 joules
  118. A 2 kilogram book sits on a shelf 3 metres above the floor. Using 10 m/s^2 for gravity, what is its gravitational potential energy?60 joules
  119. If a roller coaster car's speed doubles, its kinetic energyquadruples
  120. A pendulum swings from a high point on one side to a high point on the other, ignoring air resistance. What happens to its total mechanical energy?it stays constant, converting between kinetic and potential
  121. A skier at the top of a hill has 4000 joules of potential energy and no kinetic energy. Ignoring friction, how much kinetic energy will she have at the bottom, where potential energy is zero?4000 joules
  122. A motor does 1500 joules of work in 5 seconds. What is its power output?300 watts
  123. One horsepower is equal to about how many watts?746 watts
  124. A pump rated at 2 horsepower runs for 10 seconds. Roughly how much energy, in joules, does it deliver? Use 746 watts per horsepower.about 14,920 joules
  125. A machine takes in 500 joules of energy and produces 350 joules of useful work, the rest lost as heat. What is its mechanical efficiency?70 percent
  126. Why is the mechanical efficiency of a real gearbox always less than 100 percent?some input energy is lost to friction and heat
  127. On a first-class lever, the fulcrum is positionedbetween the effort and the load
  128. A wheelbarrow has its load in the middle, the wheel (fulcrum) at the front, and the handles (effort) at the back. What class of lever is it?second class
  129. A pair of fishing rod, where the hand grips near the fixed end and the effort is applied closer to the fulcrum than the far-off catch, is an example of which lever class?third class
  130. On a lever, moving the fulcrum closer to the load, while keeping the effort point fixed, willincrease the mechanical advantage
  131. A first-class lever has an effort arm of 8 metres and a load arm of 2 metres. What is its mechanical advantage?4
  132. A lever has a load arm of 3 metres and needs a mechanical advantage of 5. How long must the effort arm be?15 metres
  133. A seesaw is balanced with a 40 kilogram child sitting 2 metres from the fulcrum. Where must a 20 kilogram child sit on the other side to balance it?4 metres from the fulcrum
  134. A balanced first-class lever has a 60 kilogram load sitting 1.5 metres from the fulcrum. What force must be applied 3 metres from the fulcrum on the other side to balance it?30 kilograms
  135. Scissors are best described as a pair of which class of lever?first class
  136. Using a bottle opener where the rim of the cap acts as the fulcrum is an example of which class of lever?second class
  137. A nutcracker, hinged at one end with the nut placed between the arms and the hand squeezing near the far end, is an example of which lever class?second class
  138. Compared to a first-class lever with the fulcrum exactly in the middle, a third-class lever such as a broom always has a mechanical advantage that isless than 1
  139. A single fixed pulley attached to a ceiling changes the direction of a pulling force but its mechanical advantage is1
  140. A single movable pulley, attached directly to the load with the rope's other end anchored above, has a mechanical advantage of about2
  141. A pulley system has 3 rope segments supporting the moving load. What is its ideal mechanical advantage?3
  142. A block and tackle has 5 rope segments holding up a 400 newton load. Ignoring friction, what effort force is needed to lift it?80 newtons
  143. A worker pulls 60 newtons on a rope threaded through a block and tackle with 4 supporting strands. What is the maximum load this can lift, ignoring friction?240 newtons
  144. In a block and tackle with an ideal mechanical advantage of 6, what is the trade-off for the reduced effort needed to lift a load?the effort rope must be pulled 6 times farther than the load rises
  145. A block and tackle lifts a load 2 metres using a system with mechanical advantage 5. How far must the effort end of the rope be pulled?10 metres
  146. A flagpole uses a single fixed pulley at the top. Compared to lifting the flag by hand with no pulley at all, pulling the rope downrequires the same force but is more convenient because you pull downward
  147. Two setups lift the same 100 newton load: Setup A uses a single fixed pulley, Setup B uses a single movable pulley. Which setup requires less effort force?Setup B, the movable pulley
  148. A block and tackle system has a moving pulley supported by 2 strands attached to a second moving pulley supported by 2 more strands, for a total of 4 supporting strands. Ignoring friction, how much effort is needed to lift a 320 newton load?80 newtons
  149. A drive gear with 40 teeth turns a driven gear with 10 teeth. If the drive gear turns at 100 rpm, how fast does the driven gear turn?400 rpm
  150. A small gear with 12 teeth drives a large gear with 60 teeth. What is the gear ratio between them?5 to 1
  151. In a gear train with two meshing gears, if the first gear rotates clockwise, the second gear will rotatecounterclockwise
  152. A gear train has three gears meshed in a row: A drives B, and B drives C. If gear A turns clockwise, which direction does gear C turn?clockwise
  153. What is the main purpose of an idler gear placed between a drive gear and a driven gear of the same size?to make the driven gear turn the same direction as the drive gear, without changing speed
  154. A gear train has a drive gear, an idler gear, and a driven gear, all meshed in sequence. Does the idler gear change the overall gear ratio between the drive and driven gears?no, only the number of direction reversals changes
  155. A drive pulley with a 6 inch diameter is connected by a belt to a driven pulley with an 18 inch diameter. If the drive pulley spins at 300 rpm, how fast does the driven pulley spin?100 rpm
  156. Compared to a gear train, a belt and pulley drive between two shafts that are far apart has the advantage ofnot requiring the shafts to be close together or precisely aligned
  157. A gear train increases the driven gear's speed compared to the drive gear. What happens to the torque delivered to the driven gear?torque decreases
  158. A gear reduction of 4 to 1 (output turns 4 times slower than input) will make the output shaft's torque, compared to the input shaft's torque,about 4 times greater
  159. A worm gear meshing with a worm wheel is most valued in machinery because itprovides a large speed reduction and normally cannot be back-driven
  160. Two bevel gears meshed at a right angle are most useful fortransmitting rotation between two shafts that are not parallel
  161. A rack-and-pinion mechanism, such as in a car's steering system, convertsrotary motion of the pinion into straight-line motion of the rack
  162. A pinion gear with 10 teeth moves along a rack. For every full turn of the pinion, if each tooth advances the rack by 2 centimetres, how far does the rack travel?20 centimetres
  163. A ramp 12 metres long rises to a height of 3 metres. What is its ideal mechanical advantage?4
  164. Compared to lifting a heavy box straight up, pushing it up a long, gently sloped ramp requiresless force but a longer distance of travel
  165. An axe blade splitting a log is best described as an example of which simple machine?a wedge
  166. A wedge with a long, gradual taper compared to a wedge with a short, steep taper will generallyprovide greater mechanical advantage but require more distance to drive in
  167. A screw with a fine thread, many turns per inch, compared to one with a coarse thread requiresless force to turn but more turns to drive it the same distance
  168. A screw jack has a handle 40 centimetres long and a thread pitch of 0.5 centimetres per turn. What is its approximate ideal mechanical advantage?about 503
  169. Turning the large steering wheel of a ship to move a much smaller rudder shaft is a practical use of which simple machine?a wheel and axle
  170. A wheel and axle has a wheel radius of 25 centimetres and an axle radius of 5 centimetres. What is its ideal mechanical advantage?5
  171. A doorknob has a knob radius of 3 centimetres and a spindle radius of 1 centimetre. How much easier is it to turn the spindle using the knob compared to gripping the spindle directly?about 3 times easier
  172. Which pair correctly matches a simple machine with a common real-world example?wedge, an axe blade
  173. According to Pascal's principle, pressure applied to an enclosed fluid istransmitted equally in all directions throughout the fluid
  174. A hydraulic system has a small piston with area 5 square centimetres and a large piston with area 50 square centimetres. If a force of 20 newtons is applied to the small piston, what force does the large piston produce?200 newtons
  175. In the same hydraulic system, when the small piston moves down 10 centimetres, how far does the large piston move, given the areas are 5 and 50 square centimetres?1 centimetre
  176. A hydraulic piston with an area of 8 square centimetres supports a load that creates 40 newtons of force. What pressure, in newtons per square centimetre, is in the fluid?5 newtons per square centimetre
  177. Doubling the diameter of a hydraulic piston, while keeping the force applied the same, will cause the pressure it produces todecrease to one quarter of its original value
  178. According to Archimedes' principle, the buoyant force on a submerged object equalsthe weight of the fluid the object displaces
  179. A steel ship floats even though steel is denser than water becauseits hollow shape displaces enough water to equal the ship's total weight
  180. An object that is denser than the fluid it is placed in willsink, because it cannot displace enough fluid to equal its own weight
  181. Water flows through a wide section of pipe into a much narrower section. Compared to the wide section, the water's speed in the narrow section isfaster
  182. A garden hose has a flow rate of 20 litres per minute through an opening of 4 square centimetres. If a nozzle narrows the opening to 2 square centimetres, what happens to the water's exit speed?it approximately doubles
  183. A one-way check valve in a pump system is designed toallow fluid to flow in only one direction and block backflow
  184. An air compressor reduces the volume of a fixed amount of gas in a sealed tank. According to this relationship, the gas's pressure will generallyincrease, since pressure and volume are inversely related at constant temperature
  185. A support column holding up a roof is primarily under which type of stress?compression
  186. A steel cable holding up a suspended sign is primarily under which type of stress?tension
  187. A pair of scissor blades cutting through paper apply mainly which type of stress to the paper?shear
  188. A simply supported beam has a single heavy load placed exactly at its centre span between two end supports. Compared to spreading the same total load evenly along the beam, the centred point load createsgreater bending stress at the centre of the beam
  189. A four-legged table has one leg slightly shorter than the others. What is the most likely structural effect?the load is distributed unevenly, overloading the other three legs
  190. Triangular bracing is commonly used in trusses and towers because a triangle, unlike a plain rectangle,cannot change shape without one of its sides changing length
  191. An I-beam cross section is shaped with wide flanges at the top and bottom connected by a thin web. This shape is efficient becausemost of the bending resistance comes from material far from the centre, where the flanges are
  192. Compared to a stiff, brittle material, a material with high elasticity willreturn to its original shape after being deformed within its elastic limit
  193. Which generally requires more force to overcome: the static friction to start an object sliding, or the kinetic friction to keep it sliding once moving?static friction is usually greater
  194. A block requires 50 newtons of force to just begin sliding, but only 35 newtons to keep it sliding at constant speed. The 35 newton force is best described askinetic friction
  195. Adding oil between two metal surfaces that slide against each other primarily works bykeeping the surfaces separated so they do not grind directly against each other
  196. A rotating shaft supported by ball bearings, compared to the same shaft resting directly in a plain metal sleeve, will generally experienceless friction, since rolling resistance is lower than sliding friction
  197. At the bolt, a 1.5 foot wrench receives 40 pounds of applied force at its far end. What torque does this generate?60 pound-feet
  198. To loosen a very tight bolt with less applied force, a mechanic should generally use a wrench that islonger, to increase the moment arm
  199. A ball on a string is swung in a horizontal circle at increasing speed. What happens to the centripetal force needed to keep it moving in that circle?it increases as the speed increases
  200. A spring is stretched 4 centimetres by a 20 newton force. According to Hooke's law, how far will it stretch under a 40 newton force, assuming it stays within its elastic limit?8 centimetres

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