ASVAB Mechanical Comprehension Practice Test 716181 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.12
Score	0%	62%

Review

1 90 lbs. of effort is used by a machine to lift a 270 lbs. box. What is the mechanical advantage of the machine?

84% Answer Correctly

	2.7
	4.5
	3
	5

Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{270 lbs.}{90 lbs.} \) = 3

The mechanical advantage of a third class lever is always:

37% Answer Correctly

	less than one
	equal to one
	not equal to one
	greater than one

Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.

The force exerted on an object due to gravity is called:

69% Answer Correctly

	weight
	potential energy
	mass
	density

Solution

Mass is an intrinsic property of matter and does not vary. Weight is the force exerted on the mass of an object due to gravity and a specific case of Newton's Second Law of Motion. Replace force with weight and acceleration with acceleration due to gravity on Earth (g) and the result is the formula for weight: W = mg or, substituting for g, weight equals mass multiplied by 9.8 m/s².

Which of the following is not a modulus of elasticity?

47% Answer Correctly

	stress modulus
	bulk modulus
	stretch modulus
	shear modulus

Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).

5 If the green arrow in this diagram represents 250 ft⋅lb of work, how far will the box move if it weighs 50 pounds?

72% Answer Correctly

	2 ft.
	200 ft.
	5 ft.
	10 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 250 ft⋅lb and the resistance force is 50 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
250 ft⋅lb = 50 lbs. x d_resistance
d_resistance = \( \frac{250ft⋅lb}{50 lbs.} \) = 5 ft.