ASVAB Mechanical Comprehension Practice Test 93550 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.13
Score	0%	63%

Review

1 If this lever is in equilibrium with an effort force of 18.0 ft. lb. at the blue arrow and a resistance force of 9 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	0.5
	3.5
	0.45
	1

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{9 ft.}{18.0 ft.} \) = 0.5

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.5 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

Coplanar forces:

62% Answer Correctly

	act along the same line of action
	have opposite dimensions
	pass through a common point
	act in a common plane

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

3 If you lift a 47 lbs. rock 18 ft. from the ground, how much work have you done?

71% Answer Correctly

	414 ft⋅lb
	2 ft⋅lb
	None of these is correct
	846 ft⋅lb

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 47 \times 18 \)
\( W = 846 \)

Which of the following is not a type of bridge?

74% Answer Correctly

	truss
	arch
	block
	cable

Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

	efficiency
	power conversion
	mechanical advantage
	work done

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.