ASVAB Mechanical Comprehension Practice Test 323048 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.97
Score	0%	59%

Review

Concurrent forces:

55% Answer Correctly

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

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.

2 If the radius of the axle is 7 and the radius of the wheel is 12, what is the mechanical advantage of this wheel and axle configuration?

52% Answer Correctly

	7
	1.71
	12
	5

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 12 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{12}{7} \) = 1.71

3 The radius of the axle is 5, the radius of the wheel is 6, and the blue box weighs 50 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	7.2 lbs.
	5 lbs.
	6 lbs.
	41.67 lbs.

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 6 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{6}{5} \) = 1.2

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{50 lbs.}{1.2} \) = 41.67 lbs.

4 If the green arrow in this diagram represents 510 ft⋅lb of work, how far will the box move if it weighs 170 pounds?

72% Answer Correctly

	0 ft.
	3 ft.
	12 ft.
	56 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 510 ft⋅lb and the resistance force is 170 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
510 ft⋅lb = 170 lbs. x d_resistance
d_resistance = \( \frac{510ft⋅lb}{170 lbs.} \) = 3 ft.

5 A = 9 ft., the green box weighs 45 lbs., and the blue box weighs 70 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	17.36 ft.
	5.79 ft.
	23.14 ft.
	11.57 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

45 lbs. x 9 ft. = 70 lbs. x d_B

d_B = \( \frac{45 \times 9 ft⋅lb}{70 lbs.} \) = \( \frac{405 ft⋅lb}{70 lbs.} \) = 5.79 ft.