TalentLens Mechanical Comprehension 3

Question 1

A spring with a constant of 200 N/m is compressed 0.05 m. How much potential energy is stored?

Accepted Answer

0.25 J

Answer

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?

Accepted Answer

It quadruples

Answer

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?

Accepted Answer

33 lbs

Answer

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?

Accepted Answer

MA = 1

Answer

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?

Accepted Answer

50 RPM

Answer

Speed ratio = driver teeth / driven teeth = 10/40 = 1/4, so driven speed = 200 × (1/4) = 50 RPM.

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