ASVAB Mechanical Comprehension Practice Test 655269 Results

Your Results Global Average
Questions 5 5
Correct 0 2.38
Score 0% 48%

Review

1

A truck is using a rope to pull a car. Tension in the rope is greatest in which of the following places?

50% Answer Correctly

near the car

in the middle

near the truck

tension is equal in all parts of the rope
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

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

48% Answer Correctly

friction

mass

normal force

counter force
Solution

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

3 What is the power output of a 2 hp engine that's 80% efficient?
40% Answer Correctly
0 \( \frac{ft⋅lb}{s} \)
880 \( \frac{ft⋅lb}{s} \)
440 \( \frac{ft⋅lb}{s} \)
160 \( \frac{ft⋅lb}{s} \)
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 2 hp x 550 \( \frac{ft⋅lb}{s} \) = 1100 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{80 \times 1100 \frac{ft⋅lb}{s}}{100} \) \( = \frac{88000 \frac{ft⋅lb}{s}}{100} \) = 880 \( \frac{ft⋅lb}{s} \)
4

The mechanical advantage of a third class lever is always:

37% Answer Correctly

greater than one

less than one

equal to one

not equal to one
Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.

5 If 10 lbs. of force is applied 6 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?
62% Answer Correctly
30 lbs.
10 lbs.
15 lbs.
90 lbs.
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 Ra, our missing value, and plugging in our variables yields:

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{10 lbs. \times 6 ft.}{2 ft.} \) = \( \frac{60 ft⋅lb}{2 ft.} \) = 30 lbs.