Plant Operator Selection System Test Plant Operator Selection System Mechanical Concepts 4 — Questions and Answers
Question 1: An inclined plane is 10 feet long and 2 feet high. Ignoring friction, what force is required to slide a 200 lb object up the ramp?
- 20 lb
- 40 lb (Correct answer)
- 100 lb
- 200 lb
Correct answer: 40 lb
Mechanical advantage = length ÷ height = 10 ÷ 2 = 5; required force = 200 ÷ 5 = 40 lb.
Question 2: Which property of a material refers to its ability to return to its original shape after a deforming force is removed?
- Plasticity
- Ductility
- Elasticity (Correct answer)
- Hardness
Correct answer: Elasticity
Elasticity is the ability of a material to recover its original dimensions after the applied stress is removed.
Question 3: A pressure gauge on a storage tank reads 50 PSIG. The local atmospheric pressure is 14.7 PSIA. What is the absolute pressure inside the tank?
- 35.3 PSIA
- 50 PSIA
- 64.7 PSIA (Correct answer)
- 100 PSIA
Correct answer: 64.7 PSIA
Absolute pressure = gauge pressure + atmospheric pressure = 50 + 14.7 = 64.7 PSIA.
Question 4: In a V-belt drive system, what is the PRIMARY reason for maintaining proper belt tension?
- To increase the speed ratio
- To prevent slippage and ensure efficient power transfer (Correct answer)
- To reduce noise only
- To allow the belt to run without lubrication
Correct answer: To prevent slippage and ensure efficient power transfer
Proper tension prevents the belt from slipping on the pulley sheaves, which would cause power loss, heat, and accelerated belt wear.
Question 5: A reciprocating (piston) compressor differs from a centrifugal compressor primarily in that it:
- Can only compress liquids
- Uses reciprocating motion to compress gas in cylinders (Correct answer)
- Operates without valves
- Cannot achieve pressures above 100 PSI
Correct answer: Uses reciprocating motion to compress gas in cylinders
Reciprocating compressors use back-and-forth piston motion in cylinders with inlet and discharge valves to compress gas.
Question 6: When two gears mesh together, the larger gear is called the gear and the smaller is called the pinion. If the pinion has 15 teeth and the gear has 60 teeth, what is the speed ratio (gear to pinion)?
- 1:4
- 1:2
- 2:1
- 4:1 (Correct answer)
Correct answer: 4:1
The pinion rotates 4 times for every 1 rotation of the large gear, giving a 4:1 speed ratio of pinion to gear (or gear runs at ¼ pinion speed).
Question 7: What does the term 'specific gravity' of a liquid describe?
- The weight of exactly one gallon of the liquid
- The ratio of the liquid's density to the density of water (Correct answer)
- The viscosity of the liquid at room temperature
- The boiling point of the liquid compared to water
Correct answer: The ratio of the liquid's density to the density of water
Specific gravity is a dimensionless ratio comparing a substance's density to that of water (1.0), indicating whether it is lighter or heavier than water.
Plant Operator Selection System Test Plant Operator Selection System Mechanical Concepts 4
An inclined plane is 10 feet long and 2 feet high.
Ignoring friction, what force is required to slide a 200 lb object up the ramp?