Plant Operator Selection System Test Plant Operator Selection System Physics Principles 4

Question 1

Water at the bottom of a 30-foot tank exerts how much hydrostatic pressure (in psi)?

Accepted Answer

13.0 psi

Answer

Pressure = height × 0.433 psi/ft = 30 × 0.433 ≈ 13.0 psi.

Question 2

A machine does 2,000 ft-lb of work in 10 seconds. What is its power output?

Accepted Answer

0.36 hp

Answer

Power = 2000 ft-lb ÷ 10 s = 200 ft-lb/s; 1 hp = 550 ft-lb/s, so 200/550 ≈ 0.36 hp.

Question 3

When a safety relief valve opens on a boiler, it is primarily protecting against:

Accepted Answer

Excessive pressure

Answer

Relief valves are set to open at a maximum allowable working pressure to prevent catastrophic overpressure failure.

Question 4

Which of the following is a correct statement about centrifugal pumps?

Accepted Answer

Head developed increases with impeller diameter

Answer

According to affinity laws, head varies with the square of impeller speed and directly with impeller diameter increase.

Question 5

A 120-volt circuit draws 15 amps. What is the resistance of the load?

Accepted Answer

8 ohms

Answer

Ohm's Law: R = V ÷ I = 120 V ÷ 15 A = 8 ohms.

Plant Operator Selection System Test Practice Test