NFST Mechanical Aptitude 2 — Questions and Answers
Question 1: A lever is used to lift a 200-lb load. If the effort arm is 6 feet and the resistance arm is 2 feet, how much effort force is needed?
- 33 lbs
- 50 lbs
- 67 lbs (Correct answer)
- 100 lbs
Correct answer: 67 lbs
Using the lever formula: Effort × Effort Arm = Load × Resistance Arm → Effort = 200 × 2 / 6 ≈ 67 lbs.
Question 2: Which type of pulley system provides the greatest mechanical advantage?
- A single fixed pulley
- A single movable pulley
- A block and tackle with 4 rope segments (Correct answer)
- A simple wheel and axle
Correct answer: A block and tackle with 4 rope segments
A block and tackle with 4 supporting rope segments provides a mechanical advantage of 4, reducing required effort to one-fourth of the load.
Question 3: What happens to water pressure at the base of a standpipe as the height of water in the pipe increases?
- Pressure decreases
- Pressure stays the same
- Pressure increases (Correct answer)
- Pressure fluctuates randomly
Correct answer: Pressure increases
Water pressure increases with depth; every additional foot of water height adds approximately 0.434 psi to the base pressure.
Question 4: A gear with 40 teeth meshes with a gear with 10 teeth. If the larger gear rotates at 100 RPM, how fast does the smaller gear rotate?
- 25 RPM
- 100 RPM
- 250 RPM
- 400 RPM (Correct answer)
Correct answer: 400 RPM
Gear speed ratio is inverse to tooth count: 100 × (40/10) = 400 RPM for the smaller gear.
Question 5: Which of the following best describes the function of a pressure relief valve?
- It increases system pressure when flow drops
- It opens to release pressure when a set limit is exceeded (Correct answer)
- It measures fluid pressure in a system
- It converts pressure energy to kinetic energy
Correct answer: It opens to release pressure when a set limit is exceeded
A pressure relief valve automatically opens to vent excess pressure, protecting the system from damage when pressure exceeds a preset threshold.
Question 6: A firefighter uses a pry bar (a Class 1 lever) to open a door. If the fulcrum is placed very close to the door, what is the effect?
- The effort required increases significantly
- The effort required decreases significantly (Correct answer)
- Speed of movement increases at the effort end
- The mechanical advantage equals 1
Correct answer: The effort required decreases significantly
Placing the fulcrum close to the load greatly increases the effort arm relative to the resistance arm, providing high mechanical advantage and reducing effort needed.
Question 7: Two pipes carry water to a junction, then a single larger pipe carries it away. If the combined flow rate from the two input pipes equals 80 GPM, what must the output pipe carry?
- 40 GPM
- 80 GPM (Correct answer)
- 160 GPM
- It depends on pipe diameter only
Correct answer: 80 GPM
Conservation of mass requires the output flow to equal the combined input flow, so the output pipe must carry 80 GPM.
NFST Mechanical Aptitude 2
A lever is used to lift a 200-lb load.
If the effort arm is 6 feet and the resistance arm is 2 feet, how much effort force is needed?