ASVAB Mechanical Comprehension Practice Test

25 practice questions

Choose an answer, then check it under Show answer.

1. Question 1 of 25Easy

   A diver descends from a depth of 10 feet to a depth of 30 feet in a freshwater lake. How does the water pressure acting on the diver change?

   1. AA. It stays constant because liquid pressure is independent of depth.
   2. BB. It drops to zero because buoyancy cancels out liquid pressure.
   3. CC. It decreases because water pressure drops as depth increases.
   4. DD. It increases because the weight of the water column above increases.
   Show answer to question 1

   Answer: D. It increases because the weight of the water column above increases.

   Fluid pressure increases directly with depth because of the increasing weight of the liquid column pressing down from above. The idea that liquid pressure decreases or stays constant contradicts the basic hydrostatic principle that depth and pressure are directly proportional.

2. Question 2 of 25Medium

   If the net force acting on a moving cart is tripled while its total mass is doubled, what happens to the cart's acceleration?

   1. AA. It decreases to two-thirds of the original rate.
   2. BB. It increases to 1.5 times the original rate.
   3. CC. It increases to 5 times the original rate.
   4. DD. It increases to 6 times the original rate.
   Show answer to question 2

   Answer: B. It increases to 1.5 times the original rate.

   Acceleration equals net force divided by mass. Tripling the force increases acceleration by a factor of 3, but doubling the mass cuts that value in half, yielding 3 divided by 2, or 1.5 times the original rate. Multiplying the factors to get 6 times the original rate incorrectly treats mass as directly proportional to acceleration rather than inversely proportional.

3. Question 3 of 25Easy

   A mechanic rests a solid steel wrench against a hot exhaust manifold. Within a few minutes, the opposite end of the wrench becomes too hot to touch bare-handed. Which process is primarily responsible for transferring heat along the length of the tool?

   1. AA. Conduction
   2. BB. Radiation
   3. CC. Evaporation
   4. DD. Convection
   Show answer to question 3

   Answer: A. Conduction

   Conduction is the transfer of heat through direct particle-to-particle contact within a solid material. Convection is incorrect because it requires the physical movement and circulation of fluids such as liquids or gases, which cannot occur through a rigid steel wrench.

4. Question 4 of 25Medium

   A spring scale measures the downward pull of gravity directly, while a balance scale compares an object against known counterweights. If both calibrated scales are used to measure the same steel block on a planet with half of Earth's gravity, how will the readings compare to their Earth readings?

   1. AA. The spring scale reads the same, while the balance scale reads half of the Earth value.
   2. BB. Both scales read the exact same values originally measured on Earth.
   3. CC. Both scales read half of the values originally measured on Earth.
   4. DD. The balance scale reads the same, while the spring scale reads half of the Earth value.
   Show answer to question 4

   Answer: D. The balance scale reads the same, while the spring scale reads half of the Earth value.

   A balance scale determines mass by counterbalancing the unknown object with known reference masses, so a change in local gravity affects both sides equally and leaves the reading unchanged. In contrast, a spring scale measures the downward force of weight by stretching a spring, so reducing the gravitational pull by half cuts the spring deflection and measured weight in half. The belief that both scales read half overlooks the fact that balance scales compare masses rather than measuring absolute downward force.

5. Question 5 of 25Easy

   An electric motor lifts a crate to a storage loft in 30 seconds. A second motor lifts an identical crate to the same height in 15 seconds. Compared to the first motor, the second motor delivers:

   1. AA. twice as much power
   2. BB. four times as much power
   3. CC. half as much power
   4. DD. the same amount of power
   Show answer to question 5

   Answer: A. twice as much power

   Power is the rate at which work is done, defined as work divided by time. Because both motors lift identical loads through the same vertical distance, they perform the exact same amount of work. Since the second motor accomplishes this work in half the time, its power output is twice as great. Believing the power is the same confuses the total work accomplished with the rate of doing that work.

6. Question 6 of 25Hard

   A mechanic applies grease to the threads of a steel bolt before tightening it with a torque wrench to the manufacturer specification intended for dry threads. What is the effect on the bolt?

   1. AA. Bolt tension decreases, causing the fastened joint to loosen under load.
   2. BB. Bolt tension increases, creating a risk of stretching the fastener.
   3. CC. Clamping force remains unchanged because the wrench measures the same torque.
   4. DD. Thread friction increases, requiring more turns to reach the torque setting.
   Show answer to question 6

   Answer: B. Bolt tension increases, creating a risk of stretching the fastener.

   Lubricating the threads reduces rotational friction, allowing more of the applied torque to be converted into axial stretching force, which significantly increases bolt tension beyond intended design limits. The belief that clamping force remains unchanged is incorrect because torque wrenches measure rotational resistance rather than the resulting axial tension in the fastener.

7. Question 7 of 25Hard

   A solid storage crate weighing 600 pounds rests on a floor on a side measuring 2 feet by 3 feet. If the crate is turned onto another side measuring 1 foot by 2 feet, how does the pressure on the floor change?

   1. AA. It remains unchanged.
   2. BB. It is reduced to one-third.
   3. CC. It triples.
   4. DD. It doubles.
   Show answer to question 7

   Answer: C. It triples.

   Because pressure equals force divided by contact area, reducing the contact area from 6 square feet to 2 square feet while keeping the weight constant causes the pressure to increase by a factor of three. The option stating that pressure is reduced to one-third is incorrect because smaller surface areas concentrate force and increase pressure rather than decreasing it.

8. Question 8 of 25Easy

   Mechanically, a screw is classified as an inclined plane wrapped around a cylinder. What feature of the screw directly represents the inclined plane itself?

   1. AA. The spiral thread
   2. BB. The smooth shank
   3. CC. The slotted head
   4. DD. The pointed tip
   Show answer to question 8

   Answer: A. The spiral thread

   The spiral thread wrapping around the cylindrical core is an inclined plane that translates rotational motion into linear force. The pointed tip functions primarily as a wedge to pierce material rather than the continuous inclined plane. The head receives the turning tool, and an unthreaded shank provides clearance without offering mechanical advantage.

9. Question 9 of 25Hard

   A rubber suction cup is pressed firmly against a flat, smooth glass panel and holds a hanging weight. If the entire assembly is placed inside an airtight chamber and the air inside the chamber is pumped out to create a vacuum, what happens to the suction cup?

   1. AA. Its holding power decreases because external atmospheric pressure is no longer pushing it against the glass
   2. BB. Its holding power increases because fewer air molecules collide with the outer surface
   3. CC. Its holding power increases because the rubber expands outward against the surrounding glass
   4. DD. Its holding power remains unchanged because the sealed cavity under the cup maintains its original state
   Show answer to question 9

   Answer: A. Its holding power decreases because external atmospheric pressure is no longer pushing it against the glass

   A suction cup adheres because surrounding atmospheric pressure pushes it against the smooth surface with greater force than the reduced air pressure trapped underneath. When the surrounding air is evacuated, this external pushing force is removed, causing the suction cup to lose its grip and release.

10. Question 10 of 25Hard

    A compound gear train features an input gear A with 10 teeth driving gear B with 30 teeth. Gear B shares an axle with gear C, which has 20 teeth. Gear C meshes directly with output gear D, which has 80 teeth. If gear A turns at 1,200 rpm, what is the speed of gear D?

    1. AA. 800 rpm
    2. BB. 200 rpm
    3. CC. 100 rpm
    4. DD. 400 rpm
    Show answer to question 10

    Answer: C. 100 rpm

    The overall reduction ratio is found by multiplying the stage ratios together: (30 / 10) multiplied by (80 / 20) equals 3 times 4, or an overall ratio of 12 to 1. Dividing the input speed of 1,200 rpm by 12 gives an output speed of 100 rpm. The option of 400 rpm accounts only for the first gear pair and neglects the reduction produced by the second pair.

11. Question 11 of 25Medium

    A machine arm has a fixed pivot at one end. A hydraulic cylinder pushes upward at the midpoint of the arm to raise a heavy steel plate resting at the opposite end. Which class of lever is this, and what is its primary mechanical effect?

    1. AA. Third-class lever, which multiplies the input force applied by the piston.
    2. BB. Second-class lever, which reduces the effort force needed to lift the load.
    3. CC. Third-class lever, which trades force to gain movement distance at the load.
    4. DD. First-class lever, which reverses the direction of the input force.
    Show answer to question 11

    Answer: C. Third-class lever, which trades force to gain movement distance at the load.

    Because the upward effort force is applied between the pivot and the load, the linkage is a third-class lever that produces a greater range of motion and speed at the expense of requiring more input force. Identifying it as a second-class lever is incorrect because second-class levers place the load in the middle and the effort at the end to multiply force. Third-class levers never multiply force because their mechanical advantage is always less than one.

12. Question 12 of 25Hard

    A stationary container weighing 1,200 pounds hangs from an overhead crane supported by two vertical cables pulling straight upward. Cable A exerts an upward force of 750 pounds. To keep the container balanced and motionless, how much upward force must Cable B exert?

    1. AA. 1,950 pounds
    2. BB. 350 pounds
    3. CC. 600 pounds
    4. DD. 450 pounds
    Show answer to question 12

    Answer: D. 450 pounds

    For an object to remain in static equilibrium, the sum of the upward vertical forces must balance the downward gravitational force of 1,200 pounds. Subtracting Cable A's force of 750 pounds from 1,200 pounds leaves 450 pounds required from Cable B. The option of 600 pounds incorrectly assumes the load is divided equally between the two cables without accounting for Cable A's actual contribution.

13. Question 13 of 25Hard

    A solid steel pin is stuck firmly inside a hole in an aluminum bracket at room temperature. Aluminum has a higher coefficient of thermal expansion than steel. To loosen the pin for removal, how should the assembly be treated?

    1. AA. Rapidly quench the entire assembly in cold water.
    2. BB. Heat the steel pin while cooling the aluminum bracket.
    3. CC. Cool the entire assembly uniformly.
    4. DD. Heat the entire assembly uniformly.
    Show answer to question 13

    Answer: D. Heat the entire assembly uniformly.

    Because aluminum expands at a higher rate than steel, heating the entire assembly causes the hole in the bracket to enlarge more than the diameter of the steel pin, creating clearance and loosening the fit. Cooling the assembly or chilling the bracket would cause the aluminum to shrink faster than the steel, clamping down on the pin and locking it even tighter.

14. Question 14 of 25Medium

    A 500-newton crate is pushed up a frictionless ramp that is 3 meters long and rises 0.75 meter. What force, applied parallel to the ramp, is needed to move the crate up at constant speed?

    1. AA. 125 N
    2. BB. 2000 N
    3. CC. 375 N
    4. DD. 500 N
    Show answer to question 14

    Answer: A. 125 N

    The ramp's ideal mechanical advantage is 3 divided by 0.75, which is 4, so the effort is 500 newtons divided by 4, or 125 newtons. Multiplying the weight by the mechanical advantage gives 2000 newtons, but the advantage divides the load rather than increasing it.

15. Question 15 of 25Hard

    A downward force of 80 newtons is applied 0.50 meter to the left of a pivot, and a downward force of 30 newtons is applied 1.20 meters to the right of the same pivot. A downward force left of the pivot tends to rotate the lever counterclockwise, and a downward force right of the pivot tends to rotate it clockwise. What is the net torque about the pivot?

    1. AA. 76 newton-meters counterclockwise
    2. BB. 4 newton-meters clockwise
    3. CC. 40 newton-meters counterclockwise
    4. DD. 4 newton-meters counterclockwise
    Show answer to question 15

    Answer: D. 4 newton-meters counterclockwise

    The left force gives 40 newton-meters counterclockwise, and the right force gives 36 newton-meters clockwise. Because the torques oppose each other, the net torque is 4 newton-meters counterclockwise. The 76 newton-meter choice mistakenly adds the two opposing torques instead of subtracting them.

16. Question 16 of 25Easy

    A crate is pushed across a flat concrete floor. If the forward pushing force exactly equals the opposing force of friction, how will the crate move?

    1. AA. It will gradually slow down and stop.
    2. BB. It will move forward at a constant speed.
    3. CC. It will accelerate forward at a steady rate.
    4. DD. It will immediately veer to one side.
    Show answer to question 16

    Answer: B. It will move forward at a constant speed.

    When the forward pushing force and the opposing frictional force are equal, the net force is zero, meaning the forces are balanced. Under balanced forces, an object already in motion continues at a constant speed in a straight line. A common misconception is that balanced forces cause an object to slow down or stop, but a net unbalanced opposing force is required to decelerate an object.

17. Question 17 of 25Medium

    A cart is released from rest at the top of a frictionless ramp of height H and reaches a speed of 10 feet per second at the bottom. If the cart is released from rest from a new ramp that is four times as high (4H), what will its speed be at the bottom?

    1. AA. 80 feet per second
    2. BB. 40 feet per second
    3. CC. 20 feet per second
    4. DD. 14 feet per second
    Show answer to question 17

    Answer: C. 20 feet per second

    Gravitational potential energy converts directly into kinetic energy according to the formula mgh = 0.5mv^2, which simplifies to speed being proportional to the square root of height. Quadrupling the height multiplies the final speed by the square root of 4, doubling it from 10 feet per second to 20 feet per second. Predicting 40 feet per second incorrectly assumes a linear relationship between vertical drop and velocity.

18. Question 18 of 25Easy

    Pulley A and Pulley B are connected by a belt that is crossed in a figure-eight pattern. If Pulley A turns in a clockwise direction, in which direction does Pulley B turn?

    1. AA. Clockwise at a reduced speed
    2. BB. Clockwise at the same speed
    3. CC. Counterclockwise only during startup
    4. DD. Counterclockwise
    Show answer to question 18

    Answer: D. Counterclockwise

    Crossing a drive belt into a figure-eight pattern reverses the direction of rotation transmitted from the driver pulley to the driven pulley. Therefore, because Pulley A rotates clockwise, Pulley B must rotate counterclockwise. An open, uncrossed belt arrangement would cause both pulleys to rotate in the same clockwise direction.

19. Question 19 of 25Easy

    In a compound gear mechanism, two gears of different diameters are rigidly keyed to the same intermediate shaft. How do the rotational speeds and directions of these two gears compare?

    1. AA. The smaller gear rotates faster, but in the opposite direction.
    2. BB. The larger gear rotates slower, but in the same direction.
    3. CC. They rotate at the same speed and in the same direction.
    4. DD. They rotate at the same speed, but in opposite directions.
    Show answer to question 19

    Answer: C. They rotate at the same speed and in the same direction.

    Because both gears are locked to the same physical shaft, the shaft forces them to complete revolutions together at identical angular speeds and in the same rotational direction. Thinking that the larger gear rotates slower is a common mistake that applies to meshed gears on separate shafts, not gears rigidly joined on a single shaft.

20. Question 20 of 25Medium

    A rectangular crate is 0.80 m wide at its base, and its center of gravity is centered 0.60 m above the floor. It is slowly tilted about one bottom edge without sliding. At approximately what angle from upright will it begin to tip?

    1. AA. 45°
    2. BB. 34°
    3. CC. 56°
    4. DD. 53°
    Show answer to question 20

    Answer: B. 34°

    The crate tips when the weight line reaches the lower edge; using half the base width and the center-of-gravity height gives arctan(0.40/0.60), about 34 degrees. The 53-degree value comes from mistakenly using the full 0.80 m width instead of half-width.

21. Question 21 of 25Medium

    Heavy machinery frequently incorporates ball bearings between a rotating axle and its stationary housing primarily to achieve which mechanical benefit?

    1. AA. Eliminate the normal force generated by the gravitational load of the axle
    2. BB. Increase static friction to keep the axle aligned during heavy load cycles
    3. CC. Replace sliding friction with rolling friction to reduce mechanical resistance
    4. DD. Convert fluid friction into sliding friction to dissipate heat more rapidly
    Show answer to question 21

    Answer: C. Replace sliding friction with rolling friction to reduce mechanical resistance

    Ball bearings replace sliding friction with rolling friction, which generates substantially less resistive force and heat between moving parts. Bearings cannot eliminate the normal force, which is determined by the weight and load acting upon the assembly.

22. Question 22 of 25Medium

    A mechanic uses a block and tackle system containing three fixed pulleys and two movable pulleys to lift an engine weighing 450 pounds. The rope is tied directly to the movable block, passes through all pulleys, and the effort is applied by pulling downward from the last fixed pulley. Assuming 100% efficiency, how much effort force must the mechanic apply to hold the engine?

    1. AA. 90 pounds
    2. BB. 225 pounds
    3. CC. 150 pounds
    4. DD. 112.5 pounds
    Show answer to question 22

    Answer: A. 90 pounds

    When the line is anchored to the movable block, each movable pulley sheave provides two supporting strands, and the anchored line adds one more, giving five rope strands directly supporting the load. Dividing the 450-pound weight by the mechanical advantage of 5 gives an effort force of 90 pounds. The option of 112.5 pounds is incorrect because it mistakenly assumes only four supporting strands by neglecting the anchor line on the movable block.

23. Question 23 of 25Medium

    In a mechanical linkage driven by a rotating crank, a dead center position occurs when:

    1. AA. The output shaft changes its direction of rotation
    2. BB. The connecting link and crank align along the same straight line
    3. CC. The driving link experiences its highest mechanical advantage
    4. DD. The follower link attains its greatest linear speed
    Show answer to question 23

    Answer: B. The connecting link and crank align along the same straight line

    A dead center occurs when the connecting link and the crank lie in a straight line, which means an applied input force produces zero rotational torque on the crank shaft. The follower link does not reach maximum speed at this point; rather, its velocity drops to zero momentarily as it prepares to reverse direction.

24. Question 24 of 25Medium

    A mechanic pushes a rolling tool cart across a garage floor by applying a constant horizontal force of 120 newtons over a distance of 8 meters. If the move takes 4 seconds to complete, how much work is accomplished?

    1. AA. 720 J
    2. BB. 960 J
    3. CC. 480 J
    4. DD. 240 J
    Show answer to question 24

    Answer: B. 960 J

    Mechanical work depends only on the force exerted along the direction of motion multiplied by the distance traveled, giving 120 newtons multiplied by 8 meters, which equals 960 joules. The elapsed time of 4 seconds is unnecessary for calculating work, though dividing 960 joules by 4 seconds produces 240 watts, which is the power output rather than work.

25. Question 25 of 25Medium

    A lever is used to lift a 240-pound load. The distance from the fulcrum to the effort is 8 feet, and the distance from the fulcrum to the load is 2 feet. Assuming an ideal lever, what effort force is needed?

    1. AA. 40 pounds
    2. BB. 120 pounds
    3. CC. 60 pounds
    4. DD. 960 pounds
    Show answer to question 25

    Answer: C. 60 pounds

    The lever has an ideal mechanical advantage of 8 divided by 2, or 4, so the required effort is 240 pounds divided by 4, which is 60 pounds. The value 960 pounds comes from multiplying the load by the mechanical advantage instead of dividing it.

Email me my score report

The full ASVAB bank has 442 Mechanical Comprehension questions. See plans