ASVAB Mechanical Comprehension Practice Test 735317 Results

Your Results Global Average
Questions 5 5
Correct 0 3.58
Score 0% 72%

Review

1 If the green box weighs 60 lbs. and is 3 ft. from the fulcrum, how much weight would need to be placed at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 6 ft.?
63% Answer Correctly
120 lbs.
30 lbs.
0 lbs.
15 lbs.
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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{60 lbs. \times 3 ft.}{6 ft.} \) = \( \frac{180 ft⋅lb}{6 ft.} \) = 30 lbs.

2

Which of these is the formula for kinetic energy?

67% Answer Correctly

\(KE = {1 \over 2}mh^2\)

\(KE = {m \over v^2 }\)

\(KE = {1 \over 2}mv^2\)

\(KE = mgh\)
Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

3

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

wheel and axle

first-class lever

fixed pulley

block and tackle
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

4 What is the efficiency of a machine has work input of 250 ft⋅lb and work output of 237 ft⋅lb?
67% Answer Correctly
380%
190%
95%
0%
Solution
Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{237 ft⋅lb}{250 ft⋅lb} \times 100 \) \( = 95% \) %
5

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

inclined plane

third-class lever

first-class lever

second-class lever
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.