ASVAB Mechanical Comprehension Practice Test 719414 Results

Your Results Global Average
Questions 5 5
Correct 0 3.35
Score 0% 67%

Review

1

Two gears are connected and the smaller gear drives the larger gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

increase, increase

increase, decrease

decrease, increase

decrease, decrease
Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

2

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

66% Answer Correctly

dynamic load

concentrated load

static 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.

3 What is the efficiency of a machine has work input of 80 ft⋅lb and work output of 48 ft⋅lb?
67% Answer Correctly
40%
15%
0%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{48 ft⋅lb}{80 ft⋅lb} \times 100 \) \( = 60% \) %
4

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

4

0

1

2
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.

5 A = 5 ft., the green box weighs 40 lbs., and the blue box weighs 60 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
8 ft.
1.67 ft.
0.83 ft.
3.33 ft.
Solution
In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB

For this problem, the equation becomes:

40 lbs. x 5 ft. = 60 lbs. x dB

dB = \( \frac{40 \times 5 ft⋅lb}{60 lbs.} \) = \( \frac{200 ft⋅lb}{60 lbs.} \) = 3.33 ft.