ASVAB ASVAB Mechanical Comprehension Principles 5

Question 1

Two meshed spur gears have 12 teeth and 48 teeth respectively. If the small gear turns at 400 RPM, how fast does the large gear turn?

Accepted Answer

100 RPM

Answer

Gear ratio = 12/48 = 1/4, so large gear speed = 400 × (12/48) = 100 RPM.

Question 2

A pipe narrows from 4-inch diameter to 2-inch diameter. Compared to the wider section, the fluid velocity in the narrow section is:

Accepted Answer

Four times as fast

Answer

The cross-sectional area decreases by a factor of 4 (radius halved), so by continuity, velocity increases 4 times.

Question 3

Which of the following is an example of a third-class lever?

Accepted Answer

Fishing rod (effort between fulcrum and load)

Answer

In a third-class lever, the effort is applied between the fulcrum and the load, as in a fishing rod or tweezers.

Question 4

A coil spring is compressed to half its natural length. Compared to compressing it one-quarter of its natural length, the stored energy is:

Accepted Answer

Four times as much

Answer

Spring potential energy = ½kx²; doubling the compression (x) quadruples the stored energy.

Question 5

What is the primary purpose of a differential gear in a vehicle?

Accepted Answer

To allow drive wheels to rotate at different speeds during turns

Answer

The differential allows the outer wheel to rotate faster than the inner wheel when the vehicle turns a corner.

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