ASVAB Mechanical Comprehension Practice Test 202825 Results

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

Review

1

The standard unit of energy is the:

73% Answer Correctly

Watt

Volt

Joule

Horsepower
Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

2 If the green box weighs 45 lbs. and is 6 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 8 ft.?
62% Answer Correctly
67.5 lbs.
11.25 lbs.
33.75 lbs.
360 lbs.
Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{45 lbs. \times 6 ft.}{8 ft.} \) = \( \frac{270 ft⋅lb}{8 ft.} \) = 33.75 lbs.

3

Which class of lever is used to increase force on an object in the same direction as the force is applied?

53% Answer Correctly

second

first

third

all of these
Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

4 If this lever is in equilibrium with an effort force of 7.78 ft. lb. at the blue arrow and a resistance force of 7 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
0.45
0.99
2.9
0.9
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 = \( \frac{F_r}{F_e} \) = \( \frac{7 ft.}{7.78 ft.} \) = 0.9

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.9 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.

5

What type of load acts on a relatively small area of a structure?

74% Answer Correctly

dynamic load

impact load

concentrated load

non-uniformly distributed load
Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.