ASVAB Mechanical Comprehension Practice Test 199082 Results

Your Results Global Average
Questions 5 5
Correct 0 3.17
Score 0% 63%

Review

1

Drag is a type of:

81% Answer Correctly

potential energy

friction

kinetic energy

work


Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.


2 A 310 lb. barrel is rolled up a 5 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?
53% Answer Correctly
126 lbs.
124 lbs.
372 lbs.
111.6 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 5 ft. = 310 lbs. x 2 ft.
Fe = \( \frac{620 ft⋅lb}{5 ft.} \) = 124 lbs.


3 30 lbs. of effort is used by a machine to lift a 150 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
5
1
8
12

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{150 lbs.}{30 lbs.} \) = 5


4 If this lever is in equilibrium with an effort force of 7.78 ft. lb. at the blue arrow and a resistance force of 7 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
1.35
2.9
2.7
0.9

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{7 ft.}{7.78 ft.} \) = 0.9

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.9 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.


5 If you have a gear train with three gears, the first with 22 teeth, the second with 12 teeth, and the third with 8 teeth, what is its mechanical advantage?
50% Answer Correctly
1.4
0.9
3
2.8

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (Vr) 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 three gears so the equation becomes:

Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{22}{12} \) \( \frac{12}{8} \) = \( \frac{22}{8} \) = 2.8