NCEES Mechanical Engineering 2 — Questions and Answers
Question 1: In NCEES PE Mechanical practice, a shaft transmitting power P at angular velocity ω experiences a torque T equal to:
- T = Pω
- T = P/ω (Correct answer)
- T = ω/P
- T = P²/ω
Correct answer: T = P/ω
Power is the product of torque and angular velocity: P = Tω, so T = P/ω.
Question 2: According to NCEES PE Mechanical exam standards, the refrigeration cycle coefficient of performance (COP) is defined as:
- Work input divided by heat rejected
- Heat absorbed from cold reservoir divided by net work input (Correct answer)
- Heat rejected to hot reservoir divided by net work input
- Net work output divided by heat input
Correct answer: Heat absorbed from cold reservoir divided by net work input
COP for a refrigerator = QL/W_net: the desired effect (heat removed from cold space) divided by the work input.
Question 3: In NCEES Mechanical dynamics, the natural frequency of a simple spring-mass system (undamped) is:
- ωn = m/k
- ωn = √(k/m) (Correct answer)
- ωn = √(m/k)
- ωn = k·m
Correct answer: ωn = √(k/m)
The natural frequency ωn = √(k/m) in rad/s for an undamped single-degree-of-freedom system.
Question 4: For the NCEES PE Mechanical exam, the Rankine cycle efficiency is improved most effectively by:
- Lowering condenser pressure or increasing boiler temperature/pressure (Correct answer)
- Increasing condenser temperature
- Reducing pump work by using a larger pump
- Adding more stages of combustion
Correct answer: Lowering condenser pressure or increasing boiler temperature/pressure
Rankine cycle efficiency increases by raising the maximum cycle temperature/pressure or lowering the minimum (condenser) pressure.
Question 5: In NCEES PE Mechanical problems, the drag force on an object moving through a fluid is expressed as:
- FD = μAV/L
- FD = ½ρV²ACD (Correct answer)
- FD = ρgV
- FD = kAΔT
Correct answer: FD = ½ρV²ACD
Drag force FD = ½ρV²ACD, where CD is the drag coefficient, A is reference area, and ρ is fluid density.
Question 6: Which type of gear is used to transmit power between parallel shafts and is most commonly encountered in NCEES PE Mechanical exam problems?
- Bevel gear
- Worm gear
- Spur gear (Correct answer)
- Hypoid gear
Correct answer: Spur gear
Spur gears transmit power between parallel shafts and are the most fundamental gear type covered in NCEES PE Mechanical.
NCEES Mechanical Engineering 2
In NCEES PE Mechanical practice, a shaft transmitting power P at angular velocity ω experiences a torque T equal to: