ASVAB Mechanical Comprehension Practice Test 520027 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.54
Score	0%	51%

Review

Concurrent forces:

55% Answer Correctly

	act along the same line of action
	pass through a common point
	act in a common dimension
	act in a common plane

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

	do the work in 2 minutes
	do 25 ft. lb. of work in 2 minutes 5 seconds
	do the work in 3 minutes
	do 100 ft. lb. of work in 4 minutes 12 seconds

Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

	the speed of the load
	the force applied to the load
	the distance traveled by the load
	the mechanical advantage of the lever

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

4 If this lever is in equilibrium with an effort force of 11.25 ft. lb. at the blue arrow and a resistance force of 9 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	2.4
	0.8
	-8.2
	2.3

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{9 ft.}{11.25 ft.} \) = 0.8

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.8 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

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
	They have done an equal amount of work
	Sam

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.