ASVAB Mechanical Comprehension Practice Test 604272 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.35
Score	0%	47%

Review

Which of the following represents how much two materials resist sliding across each other?

53% Answer Correctly

	normal friction
	static friction
	coefficient of friction
	kinetic friction

Solution

Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

	parallel to
	along
	perpendicular to
	opposite to

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

3 What is the power output of a 6 hp engine that's 65% efficient?

40% Answer Correctly

	390 \( \frac{ft⋅lb}{s} \)
	6435 \( \frac{ft⋅lb}{s} \)
	2145 \( \frac{ft⋅lb}{s} \)
	536.3 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 6 hp x 550 \( \frac{ft⋅lb}{s} \) = 3300 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{65 \times 3300 \frac{ft⋅lb}{s}}{100} \) \( = \frac{214500 \frac{ft⋅lb}{s}}{100} \) = 2145 \( \frac{ft⋅lb}{s} \)

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

	counter force
	normal force
	mass
	friction

Solution

Normal force (F_N) represents the force a surface exerts when an object presses against it.

The mechanical advantage of a third class lever is always:

37% Answer Correctly

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