ASVAB Mechanical Comprehension Practice Test 923888 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.47
Score	0%	69%

Review

The mechanical advantage of connected gears is proportional to which characteristic of the gears?

73% Answer Correctly

	diameter
	number of teeth
	circumference
	speed

Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

2 40 lbs. of effort is used by a machine to lift a 320 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	3
	16
	8
	9.5

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{320 lbs.}{40 lbs.} \) = 8

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.

4 What is the efficiency of a machine has work input of 110 ft⋅lb and work output of 44 ft⋅lb?

67% Answer Correctly

	80%
	40%
	2%
	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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{44 ft⋅lb}{110 ft⋅lb} \times 100 \) \( = 40% \) %

Which of the following is not a characteristic of a ceramic?

61% Answer Correctly

	chemically stable
	low density
	high melting point
	low corrosive action

Solution

Ceramics are mixtures of metallic and nonmetallic elements that withstand exteme thermal, chemical, and pressure environments. They have a high melting point, low corrosive action, and are chemically stable. Examples include rock, sand, clay, glass, brick, and porcelain.