ASVAB Mechanical Comprehension Practice Test 184295 Results

Your Results Global Average
Questions 5 5
Correct 0 2.91
Score 0% 58%

Review

1 If the radius of the axle is 3 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
0.38
5
3
2.67
Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 3 and the output radius (where the resistance is being applied) is 8 for a mechanical advantage of \( \frac{3}{8} \) = 0.38

2

A fixed pulley is useful for which of the following?

53% Answer Correctly

multiplying the input force

changing the direction of the input force

multiplying the input distance

changing the direction of the output force
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

3 What is the efficiency of a machine has work input of 185 ft⋅lb and work output of 46 ft⋅lb?
67% Answer Correctly
0%
6%
75%
25%
Solution
Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{46 ft⋅lb}{185 ft⋅lb} \times 100 \) \( = 25% \) %
4

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

second-class lever

inclined plane

third-class lever

first-class lever
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

5

What type of load doesn't create specific stress points or vary with time?

60% Answer Correctly

non-uniformly distributed load

concentrated load

static uniformly distributed load

impact 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.