NFST Mechanical Aptitude 3

Question 1

A centrifugal pump is running but delivering no water. Which of the following is the most likely cause?

Accepted Answer

The pump is air-locked (not primed)

Answer

Centrifugal pumps cannot pump air; if not primed with water, they spin without moving fluid, a condition called air-lock or vapor lock.

Question 2

On a fire apparatus, what is the purpose of a pressure governor?

Accepted Answer

To maintain a preset discharge pressure automatically

Answer

A pressure governor automatically adjusts engine throttle to maintain a steady, preset discharge pressure despite changes in demand.

Question 3

A wrench handle is 12 inches long and 30 lbs of force is applied. What is the torque applied to the bolt?

Accepted Answer

30 ft-lbs

Answer

Torque = Force × Distance = 30 lbs × 1 ft (12 inches) = 30 ft-lbs.

Question 4

Which of the following materials has the highest thermal conductivity and would transfer heat most rapidly?

Accepted Answer

Copper

Answer

Copper is an excellent thermal conductor and transfers heat far more rapidly than wood, fiberglass, or rubber.

Question 5

A spring scale reads 50 lbs when an object is weighed in air, but only 40 lbs when submerged in water. What is the buoyant force acting on the object?

Accepted Answer

10 lbs

Answer

Buoyant force equals the difference between the weight in air and the apparent weight in water: 50 - 40 = 10 lbs.

NFST Test Practice Test

NFST Test Practice Test

NFST Mechanical Aptitude 3