ASVAB Mechanical Comprehension Practice Test 961001 Results

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

Review

1

What is the first step to solving a problem where multiple forces are acting on an object?

61% Answer Correctly

calculate potential energy

calculate the total force

calculate kinetic energy

calculate the net force
Solution

In mechanics, multiple forces are often acting on a particular object and, taken together, produce the net force acting on that object. Like force, net force is a vector quantity in that it has magnitude and direction.

2 What is the mechanical advantage of this inclined plane if the length of the ramp is 81 ft. and the height of the green box is 9 ft.?
82% Answer Correctly
4
3
8.1
9
Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{81 ft.}{9 ft.} \) = 9

3 What is the efficiency of a machine has work input of 120 ft⋅lb and work output of 90 ft⋅lb?
67% Answer Correctly
37%
0%
25%
75%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{90 ft⋅lb}{120 ft⋅lb} \times 100 \) \( = 75% \) %
4

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

52% Answer Correctly

third

first

all of these

second
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.

5

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

69% Answer Correctly

the number of loads

the number of connecting ropes

the number of input forces

the number of pulleys
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.