EIAT Mechanical Comprehension 2 — Questions and Answers
Question 1: A counterweight in an elevator system is used primarily to:
- Increase the speed of the cab
- Reduce the load on the hoisting motor (Correct answer)
- Prevent the cab from swaying
- Limit travel to the top floor
Correct answer: Reduce the load on the hoisting motor
Counterweights offset the weight of the cab plus a portion of rated load, reducing the energy the motor must supply.
Question 2: A sheave is best described as:
- A type of brake lining material
- A grooved pulley over which hoisting ropes run (Correct answer)
- A safety device that grips the guide rails
- A hydraulic valve that controls cab speed
Correct answer: A grooved pulley over which hoisting ropes run
A sheave is a grooved wheel (pulley) that guides and redirects wire ropes in an elevator drive system.
Question 3: If a lever has a mechanical advantage of 4 and the effort force is 50 lb, the load it can lift is:
- 12.5 lb
- 50 lb
- 200 lb (Correct answer)
- 400 lb
Correct answer: 200 lb
Mechanical advantage = Load / Effort, so Load = MA × Effort = 4 × 50 = 200 lb.
Question 4: In a hydraulic elevator, fluid pressure is applied to:
- The guide rails to reduce friction
- A piston or plunger to raise the cab (Correct answer)
- The counterweight to balance the load
- The brake drum to slow descent
Correct answer: A piston or plunger to raise the cab
Hydraulic elevators use a pump to pressurize oil that acts on a piston/plunger, which physically pushes the cab upward.
Question 5: Which type of gear provides the smoothest torque transmission and is commonly used in elevator drive machines?
- Spur gear
- Rack and pinion
- Worm gear (Correct answer)
- Bevel gear
Correct answer: Worm gear
Worm gear drives are self-locking and provide smooth, quiet operation with high reduction ratios, making them ideal for elevator machines.
Question 6: A spring under a 300 lb load compresses 2 inches. What is the spring constant (k)?
- 150 lb/in (Correct answer)
- 600 lb/in
- 60 lb/in
- 3 lb/in
Correct answer: 150 lb/in
Spring constant k = F / x = 300 lb ÷ 2 in = 150 lb/in.
Question 7: When two gears mesh, the gear with MORE teeth rotates:
- Faster than the smaller gear
- At the same speed as the smaller gear
- Slower than the smaller gear (Correct answer)
- In the same direction as the smaller gear
Correct answer: Slower than the smaller gear
In a meshed gear pair, the larger gear (more teeth) rotates more slowly; speed ratio is inversely proportional to tooth count.
EIAT Mechanical Comprehension 2
A counterweight in an elevator system is used primarily to: