TalentLens Mechanical Comprehension 3 — Questions and Answers
Question 1: A spring with a constant of 200 N/m is compressed 0.05 m. How much potential energy is stored?
- 0.025 J
- 0.25 J (Correct answer)
- 2.5 J
- 10 J
Correct answer: 0.25 J
Spring PE = ½kx² = ½ × 200 × (0.05)² = ½ × 200 × 0.0025 = 0.25 J.
Question 2: Water flows through a pipe that narrows from a 4-inch diameter to a 2-inch diameter. What happens to the water's velocity?
- It is halved
- It doubles
- It quadruples (Correct answer)
- It stays the same
Correct answer: It quadruples
Area decreases by a factor of 4 (radius halved → area quartered), so by continuity, velocity increases fourfold.
Question 3: A lever has its fulcrum at one end. A 100-lb load sits 3 ft from the fulcrum. How much force is needed 9 ft from the fulcrum to balance it?
- 300 lbs
- 33 lbs (Correct answer)
- 100 lbs
- 900 lbs
Correct answer: 33 lbs
Torque balance: 100 × 3 = F × 9, so F = 300/9 ≈ 33 lbs.
Question 4: What best describes the mechanical advantage of a single fixed pulley?
- MA = 2
- MA = 1 (Correct answer)
- MA = 0.5
- MA depends on the load
Correct answer: MA = 1
A single fixed pulley changes direction of force but provides no mechanical advantage, so MA = 1.
Question 5: A gear train has a driver gear with 10 teeth and a driven gear with 40 teeth. If the driver spins at 200 RPM, how fast does the driven gear spin?
- 800 RPM
- 200 RPM
- 50 RPM (Correct answer)
- 20 RPM
Correct answer: 50 RPM
Speed ratio = driver teeth / driven teeth = 10/40 = 1/4, so driven speed = 200 × (1/4) = 50 RPM.
Question 6: An inclined plane 10 ft long rises 2 ft. What is the ideal mechanical advantage?
- 0.2
- 2
- 5 (Correct answer)
- 8
Correct answer: 5
IMA of an inclined plane = length of slope / height = 10/2 = 5.
Question 7: Which material property allows a metal rod to return to its original shape after bending forces are removed?
- Plasticity
- Elasticity (Correct answer)
- Brittleness
- Ductility
Correct answer: Elasticity
Elasticity is the ability of a material to return to its original shape after deformation forces are removed.
TalentLens Mechanical Comprehension 3
A spring with a constant of 200 N/m is compressed 0.05 m.
How much potential energy is stored?