ASVAB Mechanical Comprehension Practice Test 938110 Results

Your Results Global Average
Questions 5 5
Correct 0 3.18
Score 0% 64%

Review

1

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

62% Answer Correctly

mass

weight

density

coefficient of friction


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.


2

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

73% Answer Correctly

torque

air pressure

liquids

gear systems


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).


3 If the green arrow in this diagram represents 850 ft⋅lb of work, how far will the box move if it weighs 170 pounds?
73% Answer Correctly
20 ft.
0 ft.
5 ft.
42 ft.

Solution
The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

Win = Wout
Feffort x deffort = Fresistance x dresistance

In this problem, the effort work is 850 ft⋅lb and the resistance force is 170 lbs. and we need to calculate the resistance distance:

Win = Fresistance x dresistance
850 ft⋅lb = 170 lbs. x dresistance
dresistance = \( \frac{850ft⋅lb}{170 lbs.} \) = 5 ft.


4 If you have a gear train with three gears, the first with 26 teeth, the second with 20 teeth, and the third with 6 teeth, what is its mechanical advantage?
51% Answer Correctly
8.7
4.3
4.8
2.2

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 = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{26}{20} \) \( \frac{20}{6} \) = \( \frac{26}{6} \) = 4.3


5

Two gears are connected and the larger gear drives the smaller gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

decrease, increase

decrease, decrease

increase, increase

increase, decrease


Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.