ASVAB Mechanical Comprehension Practice Test 836017 Results

Your Results Global Average
Questions 5 5
Correct 0 2.66
Score 0% 53%

Review

1

What type of load varies with time or affects a structure that experiences a high degree of movement?

65% Answer Correctly

impact load

dynamic load

concentrated load

static load
Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

2

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

speed or power

force or speed

force or distance

power or distance
Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

3

A fixed pulley is useful for which of the following?

53% Answer Correctly

multiplying the input force

changing the direction of the output force

changing the direction of the input force

multiplying the input distance
Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

4 If a 10 lbs. weight is placed 1 ft. from the fulcrum at the blue arrow and the green box is 6 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
0.42 lbs.
5 lbs.
1.67 lbs.
6.67 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 = \( \frac{R_bd_b}{d_a} \) = \( \frac{10 lbs. \times 1 ft.}{6 ft.} \) = \( \frac{10 ft⋅lb}{6 ft.} \) = 1.67 lbs.

5 What is the power output of a 5 hp engine that's 85% efficient?
40% Answer Correctly
17 \( \frac{ft⋅lb}{s} \)
7012.5 \( \frac{ft⋅lb}{s} \)
1168.8 \( \frac{ft⋅lb}{s} \)
2337.5 \( \frac{ft⋅lb}{s} \)
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 5 hp x 550 \( \frac{ft⋅lb}{s} \) = 2750 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{85 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{233750 \frac{ft⋅lb}{s}}{100} \) = 2337.5 \( \frac{ft⋅lb}{s} \)