ASVAB Mechanical Comprehension – Part 1
ASVAB Mechanical Comprehension
1. Which of the following is the basis for Pascal’s Law?
Correct Answer: A. The amplification of force in a hydraulic system
Pascal’s Law says pressure applied to an enclosed fluid is transmitted unchanged throughout the fluid, which allows force amplification in hydraulic systems. That is the principle behind hydraulic jacks and brakes.
2. Why does the intake valve open when the piston moves down in a pump?
Correct Answer: B. Lower pressure below the valve allows fluid in
As the piston moves down it increases the chamber volume and lowers pressure inside. Outside pressure becomes higher and pushes fluid through the intake valve into the chamber.
3. In a hydraulic lift with different piston areas, which is true?
Correct Answer: B. To do the same work, Force 2 must be smaller than Force 1 but applied over a larger distance
Pressure is the same throughout a closed hydraulic system (P = F/A). If Force 2 is smaller, it must act over a larger distance so that work (W = F × d) is conserved.
4. A fish tank is 6 ft deep, 12 ft wide, and 13 ft long. Using 1 cu ft water = 62.5 lb, what is the approximate pressure at the bottom in psi?
Correct Answer: B. 2.5
Total water weight ≈ 6×12×13 × 62.5 = 58,500 lb. Bottom area = 12×13 = 156 ft² = 22,464 in². Pressure ≈ 58,500 ÷ 22,464 ≈ 2.6 psi, so 2.5 psi is the best choice.
5. When 30 pounds of force is applied to an 8 square inch surface, what pressure is exerted?
Correct Answer: B. 3.75 psi
Pressure P = force ÷ area = 30 lb ÷ 8 in² = 3.75 psi.
6. If a person applies 200 N of force over 50 meters, how many joules of work are performed?
Correct Answer: C. 10,000 J
Work W = force × distance = 200 N × 50 m = 10,000 J.
7. Which expression correctly relates kinetic energy, mass, and velocity?
Correct Answer: C. 2(KE) = m v²
KE = ½ m v². Multiplying both sides by 2 gives 2 KE = m v², so option C is a correct rearrangement.
8. What is a component of potential energy?
Correct Answer: C. Gravity’s relationship to mass
Gravitational potential energy is PE = m g h, so gravity (g) and mass (m) are components. The energy of movement is kinetic energy, not potential.
9. If a ball is dropped from a height of 5 m, what is its approximate speed when it hits the ground? (Use g ≈ 10 m/s²)
Correct Answer: D. 10 m/s
Using conservation of energy or v² = 2 g h: v² = 2×10×5 = 100, so v = 10 m/s.
10. What does mv represent?
Correct Answer: A. Momentum
Momentum p = mass × velocity = m v.
11. What is Newton’s Third Law?
Correct Answer: D. For every action there is an equal and opposite reaction
Newton’s Third Law states forces come in equal and opposite pairs between interacting bodies.
12. Which of the following is a vector quantity?
Correct Answer: A. Gravity
Gravity is a force and has both magnitude and direction, which makes it a vector. Volume and mass are scalars.
13. What does a speedometer measure?
Correct Answer: D. Instantaneous speed
A speedometer displays the instantaneous speed at a given moment, not an average over time.
14. One horsepower is closest to how many watts?
Correct Answer: B. 746 W
By definition one mechanical horsepower ≈ 746 watts.
15. A small gear has 8 teeth and a larger gear has 16 teeth. If the larger gear makes 12 revolutions, how many revolutions does the smaller gear make?
Correct Answer: D. 24
Gear ratio = 16:8 = 2:1. The smaller gear turns twice for every turn of the larger gear. So 12 × 2 = 24 revolutions.
16. A gear with 12 teeth meshes with a gear with 4 teeth. After the larger gear completes 8 revolutions, how many revolutions will the smaller gear complete?
Correct Answer: C. 24
Teeth ratio 12:4 = 3:1. The smaller gear turns 3 times per one rotation of the larger gear. So 8 × 3 = 24.
17. Gear A (20 teeth) rotates at 60 RPM clockwise and meshes with Gear B (40 teeth). What is Gear B’s direction and speed?
Correct Answer: C. 30 RPM, counterclockwise
Meshing gears rotate in opposite directions. A has twice the speed because it has half the teeth, so B turns at half the speed: 60 ÷ 2 = 30 RPM, and opposite direction.
18. If Gear A turns counterclockwise, which other gears also turn counterclockwise? (Assume the pictured train produces alternation so that B is next to A, and B drives both C and D)
Correct Answer: A. C and D
Each meshing reverses rotation direction. If A is ccw then B is cw, and B driving C and D makes C and D ccw. Thus C and D turn ccw.
19. When torque increases, speed generally
Correct Answer: D. decreases
For a given power output, torque and angular speed are inversely related. If you increase torque (for fixed power), rotational speed tends to decrease. The exact relationship depends on system constraints, but this is the standard trade-off in mechanics and gearing.
20. A wheelbarrow is an example of which class of lever?
Correct Answer: B. Class II
A wheelbarrow is a class II lever where the load sits between fulcrum (wheel) and effort (handles).
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