ASVAB Mechanical Comprehension Practice Test 240271 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.18
Score	0%	64%

Review

1 What is the efficiency of a machine has work input of 70 ft⋅lb and work output of 31 ft⋅lb?

67% Answer Correctly

	55%
	0%
	22%
	45%

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:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{31 ft⋅lb}{70 ft⋅lb} \times 100 \) \( = 45% \) %

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	1
	2
	4
	0

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

3 If the green box weighs 10 lbs. and is 5 ft. from the fulcrum, how far from the fulcrum would a 70 lbs. force need to be applied to balance the lever?

58% Answer Correctly

	1.43 ft.
	0.36 ft.
	0.24 ft.
	0.71 ft.

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 d_b, our missing value, and plugging in our variables yields:

d_b = \( \frac{R_ad_a}{R_b} \) = \( \frac{10 lbs. \times 5 ft.}{70 lbs.} \) = \( \frac{50 ft⋅lb}{70 lbs.} \) = 0.71 ft.

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

	physics
	aeronautics
	engineering
	mechanics

Solution

Mechanics deals with motion and the forces that produce motion.

What type of load doesn't create specific stress points or vary with time?

60% Answer Correctly

	concentrated load
	impact load
	static uniformly distributed load
	non-uniformly distributed load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.