ASVAB Mechanical Comprehension Practice Test 269295 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.59
Score	0%	72%

Review

1 70 lbs. of effort is used by a machine to lift a 210 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	1
	5
	4.5
	3

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{210 lbs.}{70 lbs.} \) = 3

What is work?

60% Answer Correctly

	The movement of an object by a force
	Force per unit time
	Force per unit distance
	The potential for exertion

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

A watt is the unit for which of the following?

71% Answer Correctly

	power
	mechanical advantage
	energy
	work

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 the green arrow in this diagram represents 600 ft⋅lb of work, how far will the box move if it weighs 120 pounds?

72% Answer Correctly

	0 ft.
	30 ft.
	5 ft.
	480 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 600 ft⋅lb and the resistance force is 120 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
600 ft⋅lb = 120 lbs. x d_resistance
d_resistance = \( \frac{600ft⋅lb}{120 lbs.} \) = 5 ft.

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

73% Answer Correctly

	number of teeth
	circumference
	speed
	diameter

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.