ASVAB Mechanical Comprehension Practice Test 124049 Results

Your Results Global Average
Questions 5 5
Correct 0 2.97
Score 0% 59%

Review

1

What's the first gear in a gear train called?

57% Answer Correctly

driven gear

idler gear

driver gear

input gear


Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.


2

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

the mechanical advantage of the lever

the speed of the load

the distance traveled by the load

the force applied to the load


Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.


3 A 430 lb. barrel is rolled up a 20 ft. ramp to a platform that's 4 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
86 lbs.
94.6 lbs.
92 lbs.
87.5 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

Fede = Frdr

Plugging in the variables from this problem yields:

Fe x 20 ft. = 430 lbs. x 4 ft.
Fe = \( \frac{1720 ft⋅lb}{20 ft.} \) = 86 lbs.


4 If you have a gear train with two gears, the first with 32 teeth and the second with 8 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
4
-5
7
8

Solution

The gear ratio (Vr) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) = \( \frac{32}{8} \) = 4


5

Collinear forces:

72% Answer Correctly

pass through a common point

act in a common plane

are unrelated to each other

act along the same line of action


Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.