ASVAB Mechanical Comprehension Practice Test 742081 Results

Your Results Global Average
Questions 5 5
Correct 0 2.86
Score 0% 57%

Review

1

Lisa lifts a 25 pound box from the floor onto a loading dock 4 ft. off the ground. Sam slides the same box along a ramp to move it up another 4 ft. onto a flatbed truck. Who has done more work?

50% Answer Correctly

Neither have done any work

Lisa

Sam

They have done an equal amount of work


Solution

Work is force multiplied by distance. Because both Connie and Sam moved the same weight the same distance they have done an equal amount of work. Sam employed the mechnacial advantage of an inclined plane so he exerted less effort to do the work but the amount of work done was still the same.


2

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

57% Answer Correctly

opposite to

along

perpendicular to

parallel 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 A mass of air has a pressure of 9.0 psi and a volume of 45 ft.3. If the air is compressed to a new volume of 20 ft.3, what is the new pressure?
57% Answer Correctly
6.8 psi
11.3 psi
20.3 psi
22.3 psi

Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V2 = 20 ft.3, V1 = 45 ft.3 and P1 = 9.0 psi. Solving for P2:

P2 = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{9.0 psi}{\frac{20 ft.^3}{45 ft.^3}} \) = 20.3 psi


4

Which of the following is the formula for torque?

62% Answer Correctly

τ = F/r

τ = rF

τ = F/r2

τ = r/F


Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).


5 If the green box weighs 45 lbs. and is 1 ft. from the fulcrum, how far from the fulcrum would a 40 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
45 ft.
1.13 ft.
0.28 ft.
4.5 ft.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

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

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{45 lbs. \times 1 ft.}{40 lbs.} \) = \( \frac{45 ft⋅lb}{40 lbs.} \) = 1.13 ft.