ASVAB Mechanical Comprehension Practice Test 968180 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.88
Score	0%	58%

Review

Collinear forces:

72% Answer Correctly

	pass through a common point
	are unrelated to each other
	act along the same line of action
	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.

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	force or speed
	force or distance
	speed or power
	power or distance

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

Coplanar forces:

62% Answer Correctly

	act in a common plane
	act along the same line of action
	pass through a common point
	have opposite dimensions

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.

4 The radius of the axle is 7, the radius of the wheel is 12, and the blue box weighs 30 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	13.71 lbs.
	19 lbs.
	17.54 lbs.
	8.71 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 12 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{12}{7} \) = 1.71

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{30 lbs.}{1.71} \) = 17.54 lbs.

5 If the force applied at the blue arrow over 7 ft. moves the green box 1.0 ft., what is the mechanical advantage of this lever?

56% Answer Correctly

	2
	3
	1
	7

Solution

Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:

MA = \( \frac{E_d}{R_d} \)

where E_d is the effort distance and R_d is the resistance distance. For this problem, the equation becomes:

MA = \( \frac{7 ft.}{1.0 ft.} \) = 7

You might be wondering how having an effort distance of 7 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 7 times the resistance distance, the effort force must be \( \frac{1}{7} \) the resistance force. You're trading moving 7 times the distance for only having to use \( \frac{1}{7} \) the force.