ASVAB Mechanical Comprehension Practice Test 319718 Results

Your Results Global Average
Questions 5 5
Correct 0 2.77
Score 0% 55%

Review

1

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

conservation of mechanical energy

mechanical advantage

work-energy theorem

Pascal's law
Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

2

Which of the following represents the force a surface exerts when an object presses against it?

48% Answer Correctly

mass

counter force

friction

normal force
Solution

Normal force (FN) represents the force a surface exerts when an object presses against it.

3

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

efficiency

power conversion

work done

mechanical advantage
Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear.  For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

4 How much work can a 5 hp engine do in 6 seconds?
52% Answer Correctly
16500 ft⋅lb
0 ft⋅lb
1 ft⋅lb
2 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 5 hp \times 550 \frac{ft⋅lb}{s} \times 6s = 16500 ft⋅lb \)
5 If the green box weighs 30 lbs. and is 7 ft. from the fulcrum, how far from the fulcrum would a 10 lbs. force need to be applied to balance the lever?
58% Answer Correctly
21 ft.
84 ft.
10.5 ft.
0 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 = \( \frac{R_ad_a}{R_b} \) = \( \frac{30 lbs. \times 7 ft.}{10 lbs.} \) = \( \frac{210 ft⋅lb}{10 lbs.} \) = 21 ft.