ASVAB Mechanical Comprehension 4 — Questions and Answers
Question 1: A screw has 20 threads per inch. How far does it advance per complete revolution?
- 0.025 inches
- 0.05 inches (Correct answer)
- 0.5 inches
- 20 inches
Correct answer: 0.05 inches
Advance per revolution = 1 ÷ threads per inch = 1 ÷ 20 = 0.05 inches.
Question 2: Which simple machine is essentially an inclined plane wrapped around a cylinder?
- Wedge
- Lever
- Screw (Correct answer)
- Pulley
Correct answer: Screw
A screw is an inclined plane (ramp) wound helically around a cylindrical shaft.
Question 3: If a 10 kg box is pushed across a floor with a coefficient of kinetic friction of 0.3, what is the friction force? (g = 10 m/s²)
- 3 N
- 10 N
- 30 N (Correct answer)
- 300 N
Correct answer: 30 N
Friction force = μ × N = 0.3 × (10 × 10) = 30 N.
Question 4: In a compound pulley system with 4 rope segments supporting the load, what is the mechanical advantage?
- 1
- 2
- 4 (Correct answer)
- 8
Correct answer: 4
Mechanical advantage of a pulley system equals the number of rope segments supporting the load.
Question 5: Which valve type is best suited for fully open or fully closed flow control, not for throttling?
- Globe valve
- Gate valve (Correct answer)
- Needle valve
- Butterfly valve
Correct answer: Gate valve
Gate valves are designed for on/off service and should not be used for throttling as the gate can vibrate and erode.
Question 6: A steel beam deflects more when a load is applied at its center than at its end because:
- The center has less material
- The bending moment is greatest at the center (Correct answer)
- Steel is weaker in the middle
- The load is heavier at the center
Correct answer: The bending moment is greatest at the center
A center load on a simply supported beam creates maximum bending moment at midspan, causing greatest deflection there.
Question 7: What happens to the buoyant force on an object if it is submerged deeper in a fluid?
- It increases
- It decreases
- It stays the same (Correct answer)
- It depends on the object's weight
Correct answer: It stays the same
Buoyant force equals the weight of displaced fluid, which depends only on submerged volume, not depth.
ASVAB Mechanical Comprehension 4
A screw has 20 threads per inch.
How far does it advance per complete revolution?