EIAT Mechanical Comprehension 3 — Questions and Answers
Question 1: A 2:1 roping arrangement in a traction elevator means:
- The motor shaft turns twice for every foot the cab moves
- The cab moves at half the speed of the rope (Correct answer)
- The hoisting ropes support twice the rated load
- Two separate motors are used to raise the cab
Correct answer: The cab moves at half the speed of the rope
In 2:1 roping, the rope travels twice the distance the cab moves, so cab speed is half the rope speed but the tension in the ropes is halved.
Question 2: Kinetic energy is defined as:
- Energy stored in a compressed spring
- Energy due to an object's motion (Correct answer)
- Energy from gravitational position
- Energy released during combustion
Correct answer: Energy due to an object's motion
Kinetic energy (KE = ½mv²) is the energy an object possesses because of its velocity.
Question 3: Guide rails in an elevator hoistway serve to:
- Provide electrical grounding for the cab
- Keep the cab and counterweight aligned during travel (Correct answer)
- Support the weight of the hoisting ropes
- Act as a return path for hydraulic fluid
Correct answer: Keep the cab and counterweight aligned during travel
Guide rails constrain lateral movement of the cab and counterweight, keeping them aligned and stable throughout travel.
Question 4: Pascal's Law states that pressure applied to an enclosed fluid:
- Decreases with depth
- Is transmitted equally in all directions (Correct answer)
- Acts only in the direction of gravity
- Compresses the fluid volume proportionally
Correct answer: Is transmitted equally in all directions
Pascal's Law: pressure exerted on a confined fluid is transmitted undiminished in all directions throughout the fluid.
Question 5: Which type of rope construction is most commonly used for elevator hoisting ropes?
- Flat woven strap
- Independent wire rope core (IWRC) (Correct answer)
- Fiber core hemp rope
- Chain link assembly
Correct answer: Independent wire rope core (IWRC)
IWRC wire ropes have superior resistance to crushing and maintain their shape under load, making them the standard for elevator hoisting.
Question 6: A pump delivers 5 gallons per minute at 1,000 psi. If pressure drops to 500 psi, what happens to flow rate (assuming constant pump power)?
- Flow rate drops to 2.5 GPM
- Flow rate stays at 5 GPM
- Flow rate increases to 10 GPM (Correct answer)
- Flow rate increases to 20 GPM
Correct answer: Flow rate increases to 10 GPM
At constant power (P = Flow × Pressure), halving pressure doubles flow rate: 5 GPM × (1000/500) = 10 GPM.
Question 7: Torsion in a shaft refers to:
- Bending stress along the shaft length
- Twisting force that tends to rotate one end relative to the other (Correct answer)
- Compressive load applied to both ends
- Vibration caused by unbalanced rotating parts
Correct answer: Twisting force that tends to rotate one end relative to the other
Torsion is the twisting action in a shaft caused by an applied torque, creating shear stress in the material.
EIAT Mechanical Comprehension 3
A 2:1 roping arrangement in a traction elevator means: