NFST Mechanical Aptitude 5

Question 1

A threaded bolt has 20 threads per inch. How far does the bolt advance into a nut with each full rotation?

Accepted Answer

0.05 inches

Answer

Pitch = 1 / threads per inch = 1/20 = 0.05 inches of linear advance per full turn.

Question 2

When a fire hose is kinked, what happens to the water flow and pressure on the discharge side of the kink?

Accepted Answer

Flow decreases and pressure behind the kink increases

Answer

A kink acts like a restriction: flow downstream drops sharply while pressure builds up behind the kink on the supply side.

Question 3

Which of the following best explains why a larger diameter hose can deliver more water at the same pressure compared to a smaller hose?

Accepted Answer

Larger hose has less friction loss per unit length

Answer

Friction loss decreases dramatically as hose diameter increases, allowing greater volume flow at the same operating pressure.

Question 4

A reciprocating piston pump strokes 60 times per minute and displaces 0.5 gallons per stroke. What is its flow rate?

Accepted Answer

30 GPM

Answer

Flow rate = Strokes per minute × Displacement per stroke = 60 × 0.5 = 30 GPM.

Question 5

What is the purpose of a pressure-reducing valve in a multi-story building's standpipe system?

Accepted Answer

To prevent excessively high pressures on lower floors

Answer

Lower floors in tall buildings experience very high static pressure; pressure-reducing valves limit outlet pressure to safe, usable levels for firefighting.

NFST Test Practice Test

NFST Test Practice Test

NFST Mechanical Aptitude 5