ASVAB Mechanical Comprehension Practice Test 912592 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.37
Score	0%	67%

Review

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

73% Answer Correctly

	number of teeth
	diameter
	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 If this lever is in equilibrium with an effort force of 4.0 ft. lb. at the blue arrow and a resistance force of 2 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	1
	0.5
	0.45
	0.75

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 = \( \frac{F_r}{F_e} \) = \( \frac{2 ft.}{4.0 ft.} \) = 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.

Which of these is the formula for force?

77% Answer Correctly

	F = ma
	F = a/m
	F = am²
	F = m/a

Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

What type of load creates different stresses at different locations on a structure?

61% Answer Correctly

	impact load
	dynamic load
	non-uniformly distributed load
	static uniformly distributed load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

5 If the green arrow in this diagram represents 920 ft⋅lb of work, how far will the box move if it weighs 230 pounds?

73% Answer Correctly

	920 ft.
	460 ft.
	115 ft.
	4 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 920 ft⋅lb and the resistance force is 230 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
920 ft⋅lb = 230 lbs. x d_resistance
d_resistance = \( \frac{920ft⋅lb}{230 lbs.} \) = 4 ft.