ASVAB Mechanical Comprehension Practice Test 852651 Results

Your Results Global Average
Questions 5 5
Correct 0 3.16
Score 0% 63%

Review

1

The mass of an object correlates to the size of the object but ultimately depends on:

66% Answer Correctly

the object's density

gravity

the object's potential energy

the object's weight
Solution

Mass is a measure of the amount of matter in an object.  In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

2 What is the efficiency of a machine has work input of 55 ft⋅lb and work output of 44 ft⋅lb?
67% Answer Correctly
80%
0%
1%
160%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{44 ft⋅lb}{55 ft⋅lb} \times 100 \) \( = 80% \) %
3 How much work can a 1 hp engine do in 3 seconds?
52% Answer Correctly
2 ft⋅lb
0 ft⋅lb
1650 ft⋅lb
3 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 1 hp \times 550 \frac{ft⋅lb}{s} \times 3s = 1650 ft⋅lb \)
4 If A = 5 ft. and the green box weighs 30 lbs. what is the torque acting on the A side of this lever?
75% Answer Correctly
450 ft⋅lb
50 ft⋅lb
150 ft⋅lb
300 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 30 ft. x 5 lbs. = 150 ft⋅lb
5 The radius of the axle is 7, the radius of the wheel is 12, and the blue box weighs 90 lbs. What is the effort force necessary to balance the load?
53% Answer Correctly
52.63 lbs.
13.71 lbs.
84 lbs.
11.97 lbs.
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 12 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{12}{7} \) = 1.71

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{90 lbs.}{1.71} \) = 52.63 lbs.