NFST Mechanical Aptitude 4

Question 1

Which simple machine is a wedge most similar to in terms of mechanical principle?

Accepted Answer

An inclined plane

Answer

A wedge is essentially a moving inclined plane; both convert a smaller input force applied over a longer distance into a larger output force over a shorter distance.

Question 2

A fire pump discharges water at 150 PSI. If a nozzle is opened on a hoseline 100 feet above the pump, approximately how much pressure is lost to elevation?

Accepted Answer

43 PSI

Answer

Water loses approximately 0.434 PSI per foot of elevation: 100 ft × 0.434 ≈ 43 PSI.

Question 3

An electric motor drives a pump through a belt and pulley system. The motor pulley is 4 inches in diameter and the pump pulley is 8 inches in diameter. If the motor runs at 1800 RPM, what is the pump speed?

Accepted Answer

900 RPM

Answer

Pump speed = Motor RPM × (Motor pulley diameter / Pump pulley diameter) = 1800 × (4/8) = 900 RPM.

Question 4

What does it mean when a mechanical system has a mechanical advantage of less than 1?

Accepted Answer

The system multiplies distance but requires more input force

Answer

A mechanical advantage less than 1 means the output force is smaller than the input force, but the output moves a greater distance (trading force for speed or distance).

Question 5

Which type of valve is best suited for fully open or fully closed service and is NOT designed for throttling flow?

Accepted Answer

Gate valve

Answer

Gate valves are designed only for full-open or full-closed positions; using them for throttling causes vibration and accelerated wear.

NFST Test Practice Test

NFST Test Practice Test

NFST Mechanical Aptitude 4