ASVAB Mechanical Comprehension Practice Test 574337 Results

Your Results Global Average
Questions 5 5
Correct 0 3.51
Score 0% 70%

Review

1

A ramp is an example of which kind of simple machine?

85% Answer Correctly

inclined plane

wedge

first-class lever

none of these


Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.


2 If you have a gear train with two gears, the first with 36 teeth and the second with 4 teeth, how many revolutions does the second gear make for each revolution of the first gear?
78% Answer Correctly
9
11
27
15

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 = \( \frac{N_1}{N_2} \) = \( \frac{36}{4} \) = 9


3 If the radius of the axle is 5 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?
53% Answer Correctly
0.5
2.0
10
5

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 10 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{10}{5} \) = 2.0


4 The green box weighs 55 lbs. and a 75 lbs. weight is placed 5 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
57% Answer Correctly
6.82 ft.
11 ft.
3.41 ft.
1.7 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 da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{75 lbs. \times 5 ft.}{55 lbs.} \) = \( \frac{375 ft⋅lb}{55 lbs.} \) = 6.82 ft.


5

Tension is a force that does which of the following?

76% Answer Correctly

heats up an object

slows an object

stretches an object

compacts an object


Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.