ASVAB Mechanical Comprehension Test 5 — Questions and Answers
Question 1: A square-threaded screw has a pitch of 0.25 inches (advances 0.25 in per turn). If a 12-inch handle is used to turn it, what is the ideal mechanical advantage?
- About 48
- About 96
- About 301 (Correct answer)
- About 150
Correct answer: About 301
MA of a screw = 2π × handle length / pitch = 2π × 12 / 0.25 ≈ 301.
Question 2: Which type of stress acts perpendicular to the cross-section of a structural member and tends to pull it apart?
- Shear stress
- Compressive stress
- Tensile stress (Correct answer)
- Torsional stress
Correct answer: Tensile stress
Tensile stress acts perpendicular to a cross-section in a pulling direction, stretching the material.
Question 3: A centrifugal pump moves fluid by spinning an impeller. If the impeller's rotational speed doubles, by approximately what factor does the pump's pressure output increase?
- 2 times
- 4 times (Correct answer)
- 8 times
- 1.5 times
Correct answer: 4 times
Pump affinity laws state that pressure (head) varies as the square of rotational speed: doubling speed quadruples pressure.
Question 4: A weight hangs from two ropes attached to the ceiling. Rope A makes a 30° angle with the vertical and Rope B is vertical. Which rope carries more tension?
- Rope A (Correct answer)
- Rope B
- Both carry equal tension
- Neither — only the ceiling carries tension
Correct answer: Rope A
The angled rope must support both its share of vertical load and provide a horizontal component, giving it greater total tension than the vertical rope.
Question 5: A hydraulic press has an input cylinder with a 1-inch diameter and an output cylinder with a 5-inch diameter. If the input piston moves down 10 inches, how far does the output piston move?
- 50 inches
- 2 inches
- 0.4 inches (Correct answer)
- 5 inches
Correct answer: 0.4 inches
Volume is conserved: π(0.5)²×10 = π(2.5)²×d, solving gives d = 10×(0.25/6.25) = 0.4 inches.
Question 6: A car engine produces 200 ft-lbs of torque at 3000 RPM. What is the horsepower output?
- About 57 HP
- About 114 HP (Correct answer)
- About 200 HP
- About 86 HP
Correct answer: About 114 HP
HP = (Torque × RPM) / 5252 = (200 × 3000) / 5252 ≈ 114 HP.
Question 7: When a metal rod is heated, it expands. If both ends are rigidly fixed so it cannot expand, what type of internal stress develops?
- Tensile stress
- Shear stress
- Compressive stress (Correct answer)
- Torsional stress
Correct answer: Compressive stress
Thermal expansion is blocked, so the rod is effectively being compressed by the fixed walls, creating compressive stress.
ASVAB Mechanical Comprehension Test 5
A square-threaded screw has a pitch of 0.25 inches (advances 0.25 in per turn).
If a 12-inch handle is used to turn it, what is the ideal mechanical advantage?