ASVAB Mechanical Comprehension Practice Test 473120 Results

Your Results Global Average
Questions 5 5
Correct 0 3.28
Score 0% 66%

Review

1

A shovel is an example of which class of lever?

56% Answer Correctly

second

first

third

a shovel is not a lever


Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.


2

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

the number of pulleys

the number of loads

the number of input forces

the number of connecting ropes


Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement.  So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.


3

Which of the following is not a modulus of elasticity?

47% Answer Correctly

stretch modulus

bulk modulus

stress modulus

shear modulus


Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).


4

An object's resistance to changes in direction is known as:

82% Answer Correctly

weight

inertia

kinetic energy

mass


Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.


5 What is the efficiency of a machine has work input of 50 ft⋅lb and work output of 20 ft⋅lb?
68% Answer Correctly
40%
2%
20%
60%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{20 ft⋅lb}{50 ft⋅lb} \times 100 \) \( = 40% \) %