ASVAB Mechanical Comprehension Practice Test 671775 Results

Your Results Global Average
Questions 5 5
Correct 0 3.50
Score 0% 70%

Review

1 What is the efficiency of a machine has work input of 150 ft⋅lb and work output of 60 ft⋅lb?
67% Answer Correctly
0%
40%
80%
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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{60 ft⋅lb}{150 ft⋅lb} \times 100 \) \( = 40% \) %
2 If you lift a 11 lbs. rock 7 ft. from the ground, how much work have you done?
71% Answer Correctly
154 ft⋅lb
None of these is correct
35 ft⋅lb
77 ft⋅lb
Solution
Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 11 \times 7 \)
\( W = 77 \)
3

One Horsepower (hp) is equal to how many watts?

76% Answer Correctly

9.8

746

1492

1
Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

4 If A = 7 ft. and the green box weighs 45 lbs. what is the torque acting on the A side of this lever?
75% Answer Correctly
78 ft⋅lb
315 ft⋅lb
105 ft⋅lb
157 ft⋅lb
Solution
For a lever, torque is weight x distance from the fulcrum which, in this case, is: 45 ft. x 7 lbs. = 315 ft⋅lb
5

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

mechanical advantage

Pascal's law

conservation of mechanical energy

work-energy theorem
Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.