ASVAB Mechanical Comprehension Practice Test 62658 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.96
Score	0%	59%

Review

1 If 5 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 3 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

62% Answer Correctly

	8.33 lbs.
	1 lbs.
	2.78 lbs.
	2.08 lbs.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{5 lbs. \times 5 ft.}{3 ft.} \) = \( \frac{25 ft⋅lb}{3 ft.} \) = 8.33 lbs.

What is work?

60% Answer Correctly

	Force per unit distance
	The potential for exertion
	Force per unit time
	The movement of an object by a force

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

What's the first gear in a gear train called?

57% Answer Correctly

	driven gear
	driver gear
	input gear
	idler gear

Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.

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

	Lisa
	Sam
	They have done an equal amount of work
	Neither have done any 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.

Which of these is the formula for kinetic energy?

68% Answer Correctly

	\(KE = {1 \over 2}mv^2\)
	\(KE = {1 \over 2}mh^2\)
	\(KE = {m \over v^2 }\)
	\(KE = mgh\)

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.