ASVAB Mechanical Comprehension Practice Test 20697 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.93
Score	0%	59%

Review

1 If the radius of the axle is 5 and the radius of the wheel is 6, what is the mechanical advantage of this wheel and axle configuration?

41% Answer Correctly

	1
	1.2
	5
	0.83

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 5 and the output radius (where the resistance is being applied) is 6 for a mechanical advantage of \( \frac{5}{6} \) = 0.83

2 The green box weighs 5 lbs. and a 70 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?

57% Answer Correctly

	10.5 ft.
	1 ft.
	42 ft.
	15 ft.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{70 lbs. \times 3 ft.}{5 lbs.} \) = \( \frac{210 ft⋅lb}{5 lbs.} \) = 42 ft.

Coplanar forces:

62% Answer Correctly

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

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.

When it comes to force, mass and acceleration have what kind of relationship?

66% Answer Correctly

	exponential
	logarithmic
	inverse
	linear

Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

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

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.