IBEW Mechanical Reasoning Principles 4 — Questions and Answers
Question 1: A flywheel is used in machinery primarily to:
- Increase the gear ratio
- Store rotational energy and smooth out speed fluctuations (Correct answer)
- Convert torque to linear force
- Reduce friction between moving parts
Correct answer: Store rotational energy and smooth out speed fluctuations
A flywheel's rotational inertia stores kinetic energy, damping speed variations between power strokes.
Question 2: A screw has 16 threads per inch. How far does a nut advance along the screw for each complete turn?
- 16 inches
- 1/16 inch (Correct answer)
- 1/8 inch
- 2 inches
Correct answer: 1/16 inch
Each full revolution advances the nut one thread pitch; pitch = 1 ÷ threads per inch = 1/16 in.
Question 3: Which type of bearing is best suited for handling both radial and axial (thrust) loads simultaneously?
- Plain sleeve bearing
- Needle roller bearing
- Angular contact ball bearing (Correct answer)
- Cylindrical roller bearing
Correct answer: Angular contact ball bearing
Angular contact ball bearings are specifically designed to carry combined radial and axial loads due to their angled contact geometry.
Question 4: A centrifugal pump will lose its prime when:
- The discharge valve is fully open
- Air enters the suction side of the pump (Correct answer)
- The motor RPM is too high
- The discharge pressure exceeds the inlet pressure
Correct answer: Air enters the suction side of the pump
Air introduced to the suction side breaks the liquid column, preventing the impeller from creating the pressure differential needed to move water.
Question 5: Heat travels through the copper wires in an electrical panel primarily by:
- Convection
- Radiation
- Conduction (Correct answer)
- Evaporation
Correct answer: Conduction
Conduction is heat transfer through direct contact between molecules within a solid material like copper wire.
Question 6: A worm gear set has a 40-tooth worm wheel and a single-start worm. What is the gear ratio?
- 1:1
- 40:1 (Correct answer)
- 20:1
- 80:1
Correct answer: 40:1
For a single-start worm, the gear ratio equals the number of worm wheel teeth; here that is 40:1.
Question 7: A 12-volt battery is connected to a light bulb through a switch. The circuit is open (switch off). What is the voltage across the switch?
- 0 volts
- 6 volts
- 12 volts (Correct answer)
- Undefined
Correct answer: 12 volts
In an open circuit no current flows, so there is no voltage drop across the bulb; all 12 V appears across the open switch.
IBEW Mechanical Reasoning Principles 4
A flywheel is used in machinery primarily to: