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ASVAB Practice Test · Mechanical Comprehension

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ASVAB Practice Test Mechanical Principles Summary

Importance
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Weight
About 15 of 15 Mechanical Comprehension questions (100%)

Levers, pulleys, gears, inclined planes, pressure, and basic forces.

📖 See Mechanical Principles concepts →

Mechanical Principles: must-know points

  • Effort x effort arm = load x load arm.
  • Two meshed gears turn in opposite directions.

Mechanical Principles: 10 sample questions

Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 1. A 100-pound load sits 2 feet from the fulcrum of a lever. The effort is applied 4 feet from the fulcrum on the other side. How much effort is needed to balance the load?

  1. ① 200 pounds
  2. ② 50 pounds
  3. ③ 25 pounds
  4. ④ 100 pounds
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Answer: ② 50 pounds

Key point: Lever: effort x effort arm = load x load arm

Use the lever rule.

  1. Effort x 4 ft = 100 lb x 2 ft
  2. Effort x 4 = 200
  3. Effort = 200 / 4 = 50 lb
  4. Check: 50 x 4 = 200 and 100 x 2 = 200. Balanced.

Wrong choices

  • (A) 200 pounds: 200 comes from multiplying by the ratio the wrong way. A longer effort arm means less effort.
  • (C) 25 pounds: 25 pounds would need an effort arm 8 feet long.
  • (D) 100 pounds: 100 pounds would balance only if both arms were the same length.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 2. Gear A meshes directly with gear B. If gear A turns clockwise, which way does gear B turn?

  1. ① It does not turn
  2. ② Clockwise
  3. ③ Back and forth
  4. ④ Counterclockwise
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Answer: ④ Counterclockwise

Key point: Meshed gears turn in opposite directions

When two gears mesh, the teeth of one push the teeth of the other in the opposite direction. So if one turns clockwise, the other turns counterclockwise.

Wrong choices

  • (A) It does not turn: Meshed teeth push each other, so B must turn when A turns.
  • (B) Clockwise: Two meshed gears always turn in opposite directions, so B cannot also turn clockwise.
  • (C) Back and forth: Steady turning of A gives steady turning of B, not back-and-forth motion.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 3. What is the main advantage of using a single fixed pulley to lift a load?

  1. ① It cuts the needed force in half
  2. ② It lifts the load twice as fast
  3. ③ It changes the direction of the pulling force
  4. ④ It makes the load lighter
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Answer: ③ It changes the direction of the pulling force

Key point: Fixed pulley: changes direction, MA = 1

A single fixed pulley is attached to a support and does not move. It lets you pull down to lift a load up, which is easier, but the force needed is the same as the load's weight.

Wrong choices

  • (A) It cuts the needed force in half: Halving the force needs a movable pulley; a single fixed pulley has a mechanical advantage of 1.
  • (B) It lifts the load twice as fast: With a mechanical advantage of 1, the load moves at the same speed as the rope is pulled.
  • (D) It makes the load lighter: No pulley changes the actual weight of the load.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 4. A worker pushes a crate with a steady force of 50 pounds for a distance of 10 feet. How much work is done?

  1. ① 5 foot-pounds
  2. ② 40 foot-pounds
  3. ③ 60 foot-pounds
  4. ④ 500 foot-pounds
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Answer: ④ 500 foot-pounds

Key point: Work = force x distance

Work is force multiplied by the distance moved in the direction of the force.

  1. Work = 50 lb x 10 ft
  2. Work = 500 foot-pounds
  3. Check: 500 / 10 = 50 lb. Correct.

Wrong choices

  • (A) 5 foot-pounds: 5 comes from dividing 50 by 10. Work multiplies force by distance.
  • (B) 40 foot-pounds: 40 comes from subtracting 10 from 50.
  • (C) 60 foot-pounds: 60 comes from adding 50 + 10.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 5. Two ramps lift a box to the same height. Ramp 1 is longer than Ramp 2. Compared with Ramp 2, what does Ramp 1 require (ignoring friction)?

  1. ① Less force, but over a longer distance
  2. ② The same force over the same distance
  3. ③ More force, but over a shorter distance
  4. ④ Less force and a shorter distance
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Answer: ① Less force, but over a longer distance

Key point: Longer ramp: less force, more distance

An inclined plane trades distance for force. The work to lift the box to the same height is the same, so a longer, gentler ramp needs less force but you push it farther.

Wrong choices

  • (B) The same force over the same distance: A longer ramp is less steep, so the force needed changes.
  • (C) More force, but over a shorter distance: More force is needed on the shorter, steeper ramp, not the longer one.
  • (D) Less force and a shorter distance: A longer ramp always means a longer distance to push.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 6. A 20-tooth gear turning at 100 rpm drives a 40-tooth gear. How fast does the 40-tooth gear turn?

  1. ① 200 rpm
  2. ② 100 rpm
  3. ③ 25 rpm
  4. ④ 50 rpm
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Answer: ④ 50 rpm

Key point: Bigger driven gear turns slower

The teeth that pass the meeting point each minute are the same for both gears.

  1. Teeth per minute = 20 x 100 = 2,000
  2. Speed of the 40-tooth gear = 2,000 / 40 = 50 rpm
  3. Check: 40 x 50 = 2,000. Correct.

Wrong choices

  • (A) 200 rpm: 200 rpm would happen if the driven gear were smaller, not larger.
  • (B) 100 rpm: The speeds are equal only when both gears have the same number of teeth.
  • (C) 25 rpm: 25 rpm would need a driven gear with 80 teeth.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 7. A block and tackle has 4 rope segments supporting a 400-pound load. Ignoring friction, how much force is needed to lift the load?

  1. ① 200 pounds
  2. ② 100 pounds
  3. ③ 400 pounds
  4. ④ 1,600 pounds
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Answer: ② 100 pounds

Key point: Pulley MA = number of supporting ropes

In a pulley system, the mechanical advantage equals the number of rope segments holding up the load.

  1. Mechanical advantage = 4
  2. Force = 400 lb / 4 = 100 lb
  3. Check: 100 lb x 4 = 400 lb. Correct.

Wrong choices

  • (A) 200 pounds: 200 pounds would be the force with only 2 supporting rope segments.
  • (C) 400 pounds: 400 pounds would be needed with a mechanical advantage of 1, like a single fixed pulley.
  • (D) 1,600 pounds: 1,600 comes from multiplying 400 x 4 instead of dividing.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 8. Gear A meshes with gear B, and gear B meshes with gear C. All three are in a straight line. If gear A turns clockwise, which way does gear C turn?

  1. ① It does not turn
  2. ② Clockwise
  3. ③ Counterclockwise
  4. ④ It depends on the size of gear B
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Answer: ② Clockwise

Key point: Every other gear turns the same way

Each meshed gear reverses direction.

  1. Gear A: clockwise
  2. Gear B: counterclockwise
  3. Gear C: clockwise

A middle gear like B is called an idler gear. It makes the first and last gears turn the same way.

Wrong choices

  • (A) It does not turn: Meshed gears always pass motion along.
  • (C) Counterclockwise: Counterclockwise is the direction of gear B, the middle gear.
  • (D) It depends on the size of gear B: The size of the middle gear changes speed, not the direction of gear C.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 9. A ramp is 12 feet long and rises 3 feet. Ignoring friction, how much force is needed to push a 240-pound load up the ramp?

  1. ① 60 pounds
  2. ② 80 pounds
  3. ③ 20 pounds
  4. ④ 960 pounds
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Answer: ① 60 pounds

Key point: Ramp: force x length = weight x height

The work done pushing along the ramp equals the work of lifting straight up.

  1. Force x 12 ft = 240 lb x 3 ft
  2. Force x 12 = 720
  3. Force = 720 / 12 = 60 lb
  4. Check: 60 x 12 = 720 and 240 x 3 = 720. Correct.

Wrong choices

  • (B) 80 pounds: 80 pounds comes from dividing 240 by 3, which leaves out the ramp length.
  • (C) 20 pounds: 20 pounds comes from dividing 240 by 12, which leaves out the height.
  • (D) 960 pounds: 960 comes from multiplying 240 x 12 / 3, which is upside down.
Practice questionReviewedMechanical Comprehension › Mechanical Principles★★★★☆

Question 10. A 60-pound child sits 6 feet from the center of a seesaw. How far from the center on the other side must a 90-pound child sit to balance it?

  1. ① 9 feet
  2. ② 3 feet
  3. ③ 4 feet
  4. ④ 6 feet
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Answer: ③ 4 feet

Key point: Balance: weight x distance on both sides

The seesaw balances when weight times distance is the same on both sides.

  1. Left side: 60 lb x 6 ft = 360
  2. Right side: 90 lb x distance = 360
  3. Distance = 360 / 90 = 4 ft
  4. Check: 90 x 4 = 360. Balanced.

Wrong choices

  • (A) 9 feet: 9 feet comes from flipping the ratio; the heavier child must sit closer, not farther.
  • (B) 3 feet: At 3 feet, the 90-pound side would be too light (270 is less than 360).
  • (D) 6 feet: At 6 feet, the 90-pound side would be heavier and would go down.

Test yourself.

Mechanical Principles: 5 questions →Mechanical Comprehension: 5 questions →