ASVAB Mechanical Comprehension Practice Test 489458 Results

Your Results Global Average
Questions 5 5
Correct 0 3.10
Score 0% 62%

Review

1 If you have a gear train with three gears, the first with 26 teeth, the second with 14 teeth, and the third with 4 teeth, what is its mechanical advantage?
51% Answer Correctly
8.5
15.5
6.5
9.8

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 = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{26}{14} \) \( \frac{14}{4} \) = \( \frac{26}{4} \) = 6.5


2

Which of the following surfaces would have the lowest coefficient of friction?

85% Answer Correctly

concrete

leather

ice

tile


Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other.  Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.


3

The mechanical advantage of a third class lever is always:

37% Answer Correctly

equal to one

less than one

not equal to one

greater than one


Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.


4

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

density

coefficient of friction

mass

weight


Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.


5

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

liquids

torque

gear systems

air pressure


Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).