ASVAB Mechanical Comprehension Practice Test 772557 Results

Your Results Global Average
Questions 5 5
Correct 0 3.00
Score 0% 60%

Review

1 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle and the load is concentrated at a point 1.0 ft. from the axle, how many pounds of load will a 170 lbs. force lift?
47% Answer Correctly
None of these is correct
425
260.1
0
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: Fede = Frdr. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{170 \times 2.5}{1.0} \)
\( F_r = \frac{425.0}{1.0} \)
\( F_r = 425 \)
2 If this lever is in equilibrium with an effort force of 10.0 ft. lb. at the blue arrow and a resistance force of 2 ft. lb. at the green box, what is its mechanical advantage?
48% Answer Correctly
0.1
0.22
0.2
0.07
Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{2 ft.}{10.0 ft.} \) = 0.2

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.2 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

3 If you have a gear train with two gears, the first with 36 teeth and the second with 4 teeth, how many revolutions does the second gear make for each revolution of the first gear?
77% Answer Correctly
9.9
9
4.5
11
Solution

The gear ratio (Vr) 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:

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

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

Vr = \( \frac{N_1}{N_2} \) = \( \frac{36}{4} \) = 9

4

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

its speed

its direction

its weight

its mass
Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

5

Collinear forces:

72% Answer Correctly

act along the same line of action

act in a common plane

pass through a common point

are unrelated to each other
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.