ASVAB Mechanical Comprehension Practice Test 97526 Results

Your Results Global Average
Questions 5 5
Correct 0 2.81
Score 0% 56%

Review

1 If this lever is in equilibrium with an effort force of 4.44 ft. lb. at the blue arrow and a resistance force of 4 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
2.4
0.9
0.45
3.9
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 = \( \frac{F_r}{F_e} \) = \( \frac{4 ft.}{4.44 ft.} \) = 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.

2

A screw is most like which of the following other simple machines?

50% Answer Correctly

wheel and axle

first-class lever

inclined plane

block and tackle
Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

3

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

mechanical advantage

power

efficiency

force multiplication
Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.

4 If a 70 lbs. weight is placed 9 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
315 lbs.
630 lbs.
78.75 lbs.
19.69 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 Ra, our missing value, and plugging in our variables yields:

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{70 lbs. \times 9 ft.}{8 ft.} \) = \( \frac{630 ft⋅lb}{8 ft.} \) = 78.75 lbs.

5

What type of load varies with time or affects a structure that experiences a high degree of movement?

65% Answer Correctly

impact load

concentrated load

dynamic load

static 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.