Plant Operator Selection System Test Plant Operator Selection System Physics Principles 3 — Questions and Answers
Question 1: A fixed pulley system with one movable pulley supports a 300 lb load. Approximately how much effort force is required (ignoring friction)?
- 75 lb
- 150 lb (Correct answer)
- 300 lb
- 600 lb
Correct answer: 150 lb
A single movable pulley gives a mechanical advantage of 2, so effort = 300 ÷ 2 = 150 lb.
Question 2: Which law states that the volume of a gas is inversely proportional to its pressure at constant temperature?
- Charles's Law
- Boyle's Law (Correct answer)
- Dalton's Law
- Gay-Lussac's Law
Correct answer: Boyle's Law
Boyle's Law states P₁V₁ = P₂V₂ at constant temperature, meaning volume decreases as pressure increases.
Question 3: A steam pipe carries steam at 150 psi gauge pressure. What is the approximate absolute pressure?
- 135.7 psia
- 150 psia
- 164.7 psia (Correct answer)
- 300 psia
Correct answer: 164.7 psia
Absolute pressure = gauge pressure + atmospheric pressure (14.7 psia), so 150 + 14.7 = 164.7 psia.
Question 4: If a 10-ohm and a 20-ohm resistor are connected in parallel, what is the combined resistance?
- 30 ohms
- 15 ohms
- 6.67 ohms (Correct answer)
- 2 ohms
Correct answer: 6.67 ohms
1/R = 1/10 + 1/20 = 3/20, so R = 20/3 ≈ 6.67 ohms.
Question 5: An object is moving at 30 ft/s. If it decelerates uniformly and stops in 5 seconds, what is the deceleration?
- 3 ft/s²
- 6 ft/s² (Correct answer)
- 10 ft/s²
- 15 ft/s²
Correct answer: 6 ft/s²
Deceleration = change in velocity ÷ time = 30 ft/s ÷ 5 s = 6 ft/s².
Question 6: Which type of heat transfer does NOT require a medium and can occur through a vacuum?
- Conduction
- Convection
- Radiation (Correct answer)
- Advection
Correct answer: Radiation
Radiation transfers heat via electromagnetic waves and does not require a physical medium, unlike conduction or convection.
Question 7: If the voltage across a resistor is doubled while resistance stays the same, the power dissipated becomes:
- Doubled
- Halved
- Four times greater (Correct answer)
- Unchanged
Correct answer: Four times greater
Power = V²/R; doubling V squares it, so power increases by a factor of 4.
Plant Operator Selection System Test Plant Operator Selection System Physics Principles 3
A fixed pulley system with one movable pulley supports a 300 lb load.
Approximately how much effort force is required (ignoring friction)?