ASVAB Mechanical Comprehension Practice Test 37706 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.40
Score	0%	68%

Review

1 If you have a gear train with two gears, the first with 24 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	7.5
	1.7
	4.5
	1.5

Solution

The gear ratio (V_r) of a gear train 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 only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{24}{16} \) = 1.5

Drag is a type of:

82% Answer Correctly

	work
	kinetic energy
	friction
	potential energy

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	45 lbs
	0.83 lbs
	810 lbs
	90 lbs

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

4 If input effort is 400 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 4?

79% Answer Correctly

	0ft⋅lb
	800ft⋅lb
	6400ft⋅lb
	1600 ft⋅lb

Solution

Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 4 will multiply an input effort of 400 ft⋅lb by 4 to produce an output effort of 1600 ft⋅lb.

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

	normal force
	mass
	friction
	counter force

Solution

Normal force (F_N) represents the force a surface exerts when an object presses against it.