ASVAB Mechanical Comprehension Practice Test 143026 Results

Your Results Global Average
Questions 5 5
Correct 0 3.01
Score 0% 60%

Review

1

Which of the following is not a type of structural load?

49% Answer Correctly

live load

wind load

occupancy load

dead load
Solution

Dead load is the weight of the building and materials, live load is additional weight due to occupancy or use, snow load is the weight of accumulated snow on a structure and wind load is the force of wind pressures against structure surfaces.

2

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

fixed pulley

first-class lever

block and tackle

wheel and axle
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

3 If the green box weighs 70 lbs. and is 5 ft. from the fulcrum, how far from the fulcrum would a 70 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
5 ft.
1.25 ft.
1.67 ft.
10 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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{70 lbs. \times 5 ft.}{70 lbs.} \) = \( \frac{350 ft⋅lb}{70 lbs.} \) = 5 ft.

4

For any given surface, the coefficient of static friction is ___________ the coefficient of kinetic friction.

54% Answer Correctly

lower than

opposite

higher than

equal to
Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).

5 If this lever is in equilibrium with an effort force of 12.0 ft. lb. at the blue arrow and a resistance force of 6 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
0.5
9.5
0.45
0.25
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 = \( \frac{F_r}{F_e} \) = \( \frac{6 ft.}{12.0 ft.} \) = 0.5

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.5 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.