ASVAB Mechanical Comprehension Practice Test 376037 Results

Your Results Global Average
Questions 5 5
Correct 0 2.84
Score 0% 57%

Review

1

What's the first gear in a gear train called?

57% Answer Correctly

idler gear

driver gear

input gear

driven gear
Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.

2

Which of the following is the formula for hydraulic pressure?

58% Answer Correctly

P = F/A

P = FA

P = FA2

P = F/A2
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

Which of the following will increase the mechanical advantage of this inclined plane?

59% Answer Correctly

increase the force acting at the blue arrow

lower the force acting at the blue arrow

lengthen the ramp

shorten the ramp
Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In order to increase mechanical advantage, this ratio must increase which means making the effort distance longer and this can be accomplished by lengthening the length of the ramp.

4 If the green box weighs 50 lbs. and is 5 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 8 ft.?
63% Answer Correctly
0 lbs.
7.81 lbs.
31.25 lbs.
62.5 lbs.
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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{50 lbs. \times 5 ft.}{8 ft.} \) = \( \frac{250 ft⋅lb}{8 ft.} \) = 31.25 lbs.

5 If this lever is in equilibrium with an effort force of 25.0 ft. lb. at the blue arrow and a resistance force of 5 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
3.2
0.2
0.18
0.3
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 = \( \frac{F_r}{F_e} \) = \( \frac{5 ft.}{25.0 ft.} \) = 0.2

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.2 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.