ASVAB Mechanical Comprehension Practice Test 493911 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.39
Score	0%	68%

Review

1 What's the mechanical advantage of a wedge that's 4 inches wide and 12 inches long?

83% Answer Correctly

	4.5
	9
	3
	3.3

Solution

The mechanical advantage (MA) of a wedge is its length divided by its thickness:

MA = \( \frac{l}{t} \) = \( \frac{12 in.}{4 in.} \) = 3

Collinear forces:

72% Answer Correctly

	are unrelated to each other
	pass through a common point
	act in a common plane
	act along the same line of action

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.

Which class of lever is used to increase force on an object in the same direction as the force is applied?

53% Answer Correctly

	all of these
	third
	second
	first

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

	static friction
	kinetic friction
	gravitational friction
	dynamic friction

Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

5 If the green box weighs 30 lbs. and is 7 ft. from the fulcrum, how far from the fulcrum would a 65 lbs. force need to be applied to balance the lever?

58% Answer Correctly

	12.92 ft.
	3.23 ft.
	4 ft.
	210 ft.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{30 lbs. \times 7 ft.}{65 lbs.} \) = \( \frac{210 ft⋅lb}{65 lbs.} \) = 3.23 ft.