ASVAB Mechanical Comprehension Practice Test 587692 Results

Your Results Global Average
Questions 5 5
Correct 0 3.04
Score 0% 61%

Review

1 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 220 lbs. load concentrated at a point 0.5 ft. from the axle?
52% Answer Correctly
0
55
-51.7
440
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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{220 \times 0.5}{2.0} \)
\( F_e = \frac{110.0}{2.0} \)
\( F_e = 55 \)
2

What is the first step to solving a problem where multiple forces are acting on an object?

61% Answer Correctly

calculate the total force

calculate potential energy

calculate the net force

calculate kinetic energy
Solution

In mechanics, multiple forces are often acting on a particular object and, taken together, produce the net force acting on that object. Like force, net force is a vector quantity in that it has magnitude and direction.

3 If the green box weighs 40 lbs. and is 9 ft. from the fulcrum, how far from the fulcrum would a 15 lbs. force need to be applied to balance the lever?
58% Answer Correctly
24 ft.
12 ft.
360 ft.
96 ft.
Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{40 lbs. \times 9 ft.}{15 lbs.} \) = \( \frac{360 ft⋅lb}{15 lbs.} \) = 24 ft.

4 If the green box weighs 5 lbs. and is 9 ft. from the fulcrum, how far from the fulcrum would a 75 lbs. weight need to be placed to balance the lever?
60% Answer Correctly
45 ft.
1.8 ft.
0.6 ft.
0 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:

Rada = Rbdb

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 db, our missing value, and plugging in our variables yields:

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{5 lbs. \times 9 ft.}{75 lbs.} \) = \( \frac{45 ft⋅lb}{75 lbs.} \) = 0.6 ft.

5

The standard unit of energy is the:

73% Answer Correctly

Horsepower

Joule

Watt

Volt
Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).