ASVAB Mechanical Comprehension Practice Test 812438 Results

Your Results Global Average
Questions 5 5
Correct 0 2.94
Score 0% 59%

Review

1

Tension is a force that does which of the following?

75% Answer Correctly

slows an object

compacts an object

heats up an object

stretches an object
Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.

2

The mass of an object correlates to the size of the object but ultimately depends on:

66% Answer Correctly

the object's potential energy

the object's weight

gravity

the object's density
Solution

Mass is a measure of the amount of matter in an object.  In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

3 What is the power output of a 8 hp engine that's 70% efficient?
40% Answer Correctly
1540 \( \frac{ft⋅lb}{s} \)
1026.7 \( \frac{ft⋅lb}{s} \)
8 \( \frac{ft⋅lb}{s} \)
3080 \( \frac{ft⋅lb}{s} \)
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 8 hp x 550 \( \frac{ft⋅lb}{s} \) = 4400 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{70 \times 4400 \frac{ft⋅lb}{s}}{100} \) \( = \frac{308000 \frac{ft⋅lb}{s}}{100} \) = 3080 \( \frac{ft⋅lb}{s} \)
4

A screw is most like which of the following other simple machines?

50% Answer Correctly

inclined plane

block and tackle

wheel and axle

first-class lever
Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

5 The green box weighs 10 lbs. and a 65 lbs. weight is placed 7 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
57% Answer Correctly
22.75 ft.
11.38 ft.
15.17 ft.
45.5 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 da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{65 lbs. \times 7 ft.}{10 lbs.} \) = \( \frac{455 ft⋅lb}{10 lbs.} \) = 45.5 ft.