FCTC Mechanical Reasoning Principles Questions and Answers 5 — Questions and Answers
Question 1: A centrifugal pump's impeller speed is doubled. By approximately what factor does the pump's flow rate change?
- 2× (Correct answer)
- 4×
- 8×
- 1× (no change)
Correct answer: 2×
By the centrifugal pump affinity laws, flow rate is directly proportional to impeller speed.
Question 2: Which material would be the best thermal insulator in a mechanical system?
- Fiberglass (Correct answer)
- Aluminum
- Steel
- Copper
Correct answer: Fiberglass
Fiberglass has very low thermal conductivity, making it an excellent insulator compared to metals.
Question 3: A shaft transmits 10 hp at 1,000 RPM. If the speed is reduced to 500 RPM while maintaining the same power, the torque will:
- Double (Correct answer)
- Halve
- Stay the same
- Quadruple
Correct answer: Double
Power = Torque × Speed; if speed halves and power stays constant, torque must double.
Question 4: A pipe joint leaks when pressure increases. The most likely cause is:
- A failed or worn gasket (Correct answer)
- Excessive pipe wall thickness
- Too many pipe threads
- High ambient humidity
Correct answer: A failed or worn gasket
Gaskets create the seal between pipe flanges; a worn or damaged gasket will fail under increased pressure.
Question 5: In a simple electrical circuit, if the resistance is doubled while voltage stays the same, the current will:
- Be halved (Correct answer)
- Double
- Stay the same
- Quadruple
Correct answer: Be halved
By Ohm's Law, I = V/R; if R doubles and V is constant, current (I) is cut in half.
Question 6: A ball valve is preferred over a globe valve when the primary requirement is:
- Full-open or full-closed shutoff with minimal pressure drop (Correct answer)
- Precise flow throttling
- High-temperature steam service
- Handling of slurries
Correct answer: Full-open or full-closed shutoff with minimal pressure drop
Ball valves open fully with a quarter-turn, offering very low pressure drop and fast shutoff.
Question 7: A class 2 lever has the load between the fulcrum and the effort. A common example is:
- A wheelbarrow (Correct answer)
- A pair of scissors
- A seesaw
- A fishing rod
Correct answer: A wheelbarrow
In a wheelbarrow, the wheel is the fulcrum, the load sits in the bin between the wheel and the handles where effort is applied.
FCTC Mechanical Reasoning Principles Questions and Answers 5
A centrifugal pump's impeller speed is doubled.
By approximately what factor does the pump's flow rate change?