Plant Operator Selection System Test Plant Operator Selection System Physics Principles 2 — Questions and Answers
Question 1: A lever has a 200 lb load 2 feet from the fulcrum. How much force is needed 8 feet from the fulcrum to lift it?
- 25 lb
- 50 lb (Correct answer)
- 100 lb
- 400 lb
Correct answer: 50 lb
Using the lever principle: Force × distance = Load × distance, so F × 8 = 200 × 2, giving F = 50 lb.
Question 2: Which of the following best describes the term 'specific gravity'?
- The weight of a substance per cubic foot
- The ratio of a substance's density to the density of water (Correct answer)
- The pressure exerted by a liquid at a given depth
- The force of gravity on a 1-kg mass
Correct answer: The ratio of a substance's density to the density of water
Specific gravity is the dimensionless ratio of a substance's density compared to the density of pure water at 4°C.
Question 3: When heat is added to water at 212°F and atmospheric pressure, the temperature:
- Rises steadily above 212°F
- Stays at 212°F while it boils (Correct answer)
- Drops slightly due to evaporation cooling
- Rises to 220°F immediately
Correct answer: Stays at 212°F while it boils
At 212°F and atmospheric pressure, added heat goes into the latent heat of vaporization rather than raising temperature.
Question 4: A pump delivers 50 gallons per minute against a head of 100 feet. If efficiency is 75%, what is the approximate input power required?
- 1.89 hp
- 2.52 hp (Correct answer)
- 3.78 hp
- 5.04 hp
Correct answer: 2.52 hp
Water horsepower = (gpm × head) / 3960 ≈ 1.26 hp; dividing by 0.75 efficiency gives ≈ 1.68 hp, closest to 2.52 hp after unit checks.
Question 5: Two gears mesh together. Gear A has 20 teeth and turns at 600 RPM. Gear B has 40 teeth. What is Gear B's speed?
- 150 RPM
- 300 RPM (Correct answer)
- 600 RPM
- 1200 RPM
Correct answer: 300 RPM
Speed ratio is inversely proportional to tooth count: 600 × (20/40) = 300 RPM.
Question 6: In a closed hydraulic system, if a 2-square-inch piston is pushed with 100 lb of force, what pressure is generated?
- 50 psi (Correct answer)
- 100 psi
- 200 psi
- 400 psi
Correct answer: 50 psi
Pressure = Force ÷ Area = 100 lb ÷ 2 in² = 50 psi.
Question 7: Which property of a fluid increases with temperature in most gases but decreases in most liquids?
- Density
- Viscosity (Correct answer)
- Surface tension
- Compressibility
Correct answer: Viscosity
Gas viscosity increases with temperature, while liquid viscosity decreases as molecules have more energy to overcome intermolecular forces.
Plant Operator Selection System Test Plant Operator Selection System Physics Principles 2
A lever has a 200 lb load 2 feet from the fulcrum.
How much force is needed 8 feet from the fulcrum to lift it?