ASVAB Mechanical Comprehension Practice Test 20074 Results

Your Results Global Average
Questions 5 5
Correct 0 3.26
Score 0% 65%

Review

1 What is the power output of a 3 hp engine that's 35% efficient?
39% Answer Correctly
577.5 \( \frac{ft⋅lb}{s} \)
288.8 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
2310 \( \frac{ft⋅lb}{s} \)
Solution
\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), Pi becomes 3 hp x 550 \( \frac{ft⋅lb}{s} \) = 1650 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{35 \times 1650 \frac{ft⋅lb}{s}}{100} \) \( = \frac{57750 \frac{ft⋅lb}{s}}{100} \) = 577.5 \( \frac{ft⋅lb}{s} \)
2 10 lbs. of effort is used by a machine to lift a 20 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
5
3
2.2
2
Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{20 lbs.}{10 lbs.} \) = 2

3 If a 70 lbs. weight is placed 3 ft. from the fulcrum at the blue arrow and the green box is 2 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
210 lbs.
52.5 lbs.
420 lbs.
105 lbs.
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 Ra, our missing value, and plugging in our variables yields:

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{70 lbs. \times 3 ft.}{2 ft.} \) = \( \frac{210 ft⋅lb}{2 ft.} \) = 105 lbs.

4

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

66% Answer Correctly

linear

logarithmic

inverse

exponential
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.

5

Which of the following is not a type of bridge?

74% Answer Correctly

arch

block

cable

truss
Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.