ASVAB Mechanical Comprehension Practice Test 5338 Results

Your Results Global Average
Questions 5 5
Correct 0 3.25
Score 0% 65%

Review

1 What is the efficiency of a machine has work input of 175 ft⋅lb and work output of 78 ft⋅lb?
67% Answer Correctly
45%
22%
0%
55%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{78 ft⋅lb}{175 ft⋅lb} \times 100 \) \( = 45% \) %
2 If A = 9 ft. and the green box weighs 25 lbs. what is the torque acting on the A side of this lever?
74% Answer Correctly
75 ft⋅lb
450 ft⋅lb
56 ft⋅lb
225 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 25 ft. x 9 lbs. = 225 ft⋅lb
3

Normal force is generally equal to the __________ of an object.

61% Answer Correctly

mass

density

weight

coefficient of friction
Solution

Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.

4 If the green box weighs 40 lbs. and is 5 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 7 ft.?
62% Answer Correctly
28.57 lbs.
14.29 lbs.
0 lbs.
114.29 lbs.
Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{40 lbs. \times 5 ft.}{7 ft.} \) = \( \frac{200 ft⋅lb}{7 ft.} \) = 28.57 lbs.

5

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

non-uniformly distributed load

dynamic 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.