ASVAB Mechanical Comprehension Practice Test 331257 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.71
Score	0%	54%

Review

1 If you have a gear train with three gears, the first with 28 teeth, the second with 10 teeth, and the third with 8 teeth, what is its mechanical advantage?

51% Answer Correctly

	5.3
	7
	10.5
	3.5

Solution

The mechanical advantage of a gear train is its gear ratio. The gear ratio (V_r) is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have three gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{28}{10} \) \( \frac{10}{8} \) = \( \frac{28}{8} \) = 3.5

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

	\(PE = mgh\)
	\(PE = { 1 \over 2} mv^2\)
	\(PE = mg^2h\)
	\(PE = { 1 \over 2} mg^2\)

Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s²).

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
	Sam
	They have done an equal amount of work
	Lisa

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.

4 How much work can a 2 hp engine do in 4 seconds?

52% Answer Correctly

	1 ft⋅lb
	2 ft⋅lb
	4400 ft⋅lb
	4 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 2 hp \times 550 \frac{ft⋅lb}{s} \times 4s = 4400 ft⋅lb \)

An inclined plane increases ___________ to reduce ____________.

58% Answer Correctly

	distance, power
	force, distance
	distance, force
	force, power

Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.