EIAT Forces, Torque, and Motion 4 ā Questions and Answers
Question 1: An elevator rope stretches 0.02 m under a load of 4,000 N. If the spring constant of the rope is k, what is k?
- 80 N/m
- 200 N/m
- 80,000 N/m
- 200,000 N/m (Correct answer)
Correct answer: 200,000 N/m
k = F / x = 4,000 / 0.02 = 200,000 N/m.
Question 2: An elevator car travels 30 m upward in 15 seconds at constant speed. What is its velocity?
- 0.5 m/s
- 2 m/s (Correct answer)
- 15 m/s
- 45 m/s
Correct answer: 2 m/s
Velocity = distance / time = 30 / 15 = 2 m/s.
Question 3: A 750 kg car is supported by a rope with 2:1 roping. What tension acts in each rope segment supporting the car?
- 375 N
- 3,675 N (Correct answer)
- 7,350 N
- 14,700 N
Correct answer: 3,675 N
With 2:1 roping, the car weight (750 Ć 9.8 = 7,350 N) is split across 2 rope segments: 7,350 / 2 = 3,675 N each.
Question 4: Which of the following increases the torque applied to a bolt without changing the applied force?
- Using a shorter wrench
- Using a longer wrench (Correct answer)
- Tightening faster
- Reducing friction on the bolt
Correct answer: Using a longer wrench
Torque = Force Ć lever arm; a longer wrench increases the lever arm, increasing torque for the same force.
Question 5: A force of 200 N acts on an object at a 30Ā° angle to the horizontal. What is the horizontal component of this force?
- 100 N
- 141 N
- 173 N (Correct answer)
- 200 N
Correct answer: 173 N
Horizontal component = 200 Ć cos 30Ā° = 200 Ć 0.866 ā 173 N.
Question 6: What happens to the tension in a hoisting rope when the elevator decelerates while moving upward?
- Tension increases above the static load
- Tension equals the static load
- Tension decreases below the static load (Correct answer)
- Tension drops to zero
Correct answer: Tension decreases below the static load
Decelerating while moving upward means net acceleration is downward, reducing the rope tension below the car's static weight.
Question 7: A flywheel stores energy primarily as:
- Potential energy
- Thermal energy
- Rotational kinetic energy (Correct answer)
- Elastic potential energy
Correct answer: Rotational kinetic energy
A flywheel stores energy in its spinning mass as rotational kinetic energy (Ā½IĻĀ²).
EIAT Forces, Torque, and Motion 4
An elevator rope stretches 0.02 m under a load of 4,000 N.
If the spring constant of the rope is k, what is k?