ASVAB Mechanical Comprehension Practice Test 883889 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.72
Score	0%	54%

Review

1 If A = 9 ft. and the green box weighs 50 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	1350 ft⋅lb
	1800 ft⋅lb
	900 ft⋅lb
	450 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 50 ft. x 9 lbs. = 450 ft⋅lb

2 What is the efficiency of a machine has work input of 110 ft⋅lb and work output of 71 ft⋅lb?

67% Answer Correctly

	130%
	65%
	260%
	16%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{71 ft⋅lb}{110 ft⋅lb} \times 100 \) \( = 65% \) %

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

	acceleration
	total mechanical energy
	potential energy
	kinetic energy

Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

Which of the following is not a modulus of elasticity?

47% Answer Correctly

	shear modulus
	stretch modulus
	bulk modulus
	stress 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).

Force of friction due to kinetic friction is __________ the force of friction due to static friction.

40% Answer Correctly

	the same as
	lower than
	opposite
	higher than

Solution

The formula for force of friction (F_f) is the same whether kinetic or static friction applies: F_{f =}μF_N. To distinguish between kinetic and static friction, μ_k and μ_s are often used in place of μ.