ASVAB Mechanical Comprehension Practice Test 732236 Results

Your Results Global Average
Questions 5 5
Correct 0 3.40
Score 0% 68%

Review

1 If you have a gear train with two gears, the first with 20 teeth and the second with 4 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
15
1.7
6.5
5
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 = \( \frac{N_1}{N_2} \) = \( \frac{20}{4} \) = 5

2 If the green box weighs 5 lbs. and is 9 ft. from the fulcrum, how far from the fulcrum would a 35 lbs. weight need to be placed to balance the lever?
60% Answer Correctly
0.43 ft.
1.29 ft.
1 ft.
3.86 ft.
Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{5 lbs. \times 9 ft.}{35 lbs.} \) = \( \frac{45 ft⋅lb}{35 lbs.} \) = 1.29 ft.

3 What's the mechanical advantage of a wedge that's 2 inches wide and 10 inches long?
83% Answer Correctly
5.5
8
5
7
Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{10 in.}{2 in.} \) = 5

4

Which of the following is not a type of bridge?

74% Answer Correctly

truss

arch

block

cable
Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

5 A mass of air has a pressure of 6.0 psi and a volume of 30 ft.3. If the air is compressed to a new volume of 15 ft.3, what is the new pressure?
56% Answer Correctly
36 psi
15 psi
12 psi
14 psi
Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V2 = 15 ft.3, V1 = 30 ft.3 and P1 = 6.0 psi. Solving for P2:

P2 = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{6.0 psi}{\frac{15 ft.^3}{30 ft.^3}} \) = 12 psi