ASVAB Mechanical Comprehension Practice Test 577415 Results

Your Results Global Average
Questions 5 5
Correct 0 2.64
Score 0% 53%

Review

1

The principle of moments defines equilibrium in terms of:

53% Answer Correctly

torque

power

energy

speed
Solution

According to the principle of moments, you can maintain equilibrium if the moments (forces) tending to clockwise rotation are equal to the moments tending to counterclockwise rotation. Another name for these moments of force is torque.

2

Collinear forces:

72% Answer Correctly

pass through a common point

act in a common plane

are unrelated to each other

act along the same line of action
Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

3 What is the power output of a 8 hp engine that's 85% efficient?
40% Answer Correctly
3740 \( \frac{ft⋅lb}{s} \)
11220 \( \frac{ft⋅lb}{s} \)
10 \( \frac{ft⋅lb}{s} \)
14960 \( \frac{ft⋅lb}{s} \)
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 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{85 \times 4400 \frac{ft⋅lb}{s}}{100} \) \( = \frac{374000 \frac{ft⋅lb}{s}}{100} \) = 3740 \( \frac{ft⋅lb}{s} \)
4

Assuming force applied remains constant, which of the following will result in more work being done?

53% Answer Correctly

moving the object with more speed

moving the object with more acceleration

increasing the coefficient of friction

moving the object farther
Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done.

5 If A = 11 ft., B = 2 ft., C = 6 ft., the green box weighs 45 lbs. and the blue box weighs 55 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
192.5 lbs.
0 lbs.
16.04 lbs.
64.17 lbs.
Solution
In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

45 lbs. x 11 ft. = 55 lbs. x 2 ft. + fC x 6 ft.

495 ft. lbs. = 110 ft. lbs. + fC x 6 ft.

fC = \( \frac{495 ft. lbs. - 110 ft. lbs.}{6 ft.} \) = \( \frac{385 ft. lbs.}{6 ft.} \) = 64.17 lbs.