ASVAB Mechanical Comprehension Practice Test 770163 Results

Your Results Global Average
Questions 5 5
Correct 0 2.43
Score 0% 49%

Review

1 How much work can a 7 hp engine do in 10 seconds?
52% Answer Correctly
1 ft⋅lb
14 ft⋅lb
38500 ft⋅lb
28 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 7 hp \times 550 \frac{ft⋅lb}{s} \times 10s = 38500 ft⋅lb \)
2 If A = 9 ft., B = 3 ft., C = 6 ft., the green box weighs 50 lbs. and the blue box weighs 65 lbs., what does the orange box have to weigh for this lever to balance?
43% Answer Correctly
0 lbs.
150 lbs.
42.5 lbs.
14.17 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:

50 lbs. x 9 ft. = 65 lbs. x 3 ft. + fC x 6 ft.

450 ft. lbs. = 195 ft. lbs. + fC x 6 ft.

fC = \( \frac{450 ft. lbs. - 195 ft. lbs.}{6 ft.} \) = \( \frac{255 ft. lbs.}{6 ft.} \) = 42.5 lbs.

3

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

54% Answer Correctly

increase applied force

decrease torque

decrease applied force

increase torque
Solution

Torque measures force applied during rotation: τ = rF.  Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

4

The mechanical advantage of a third class lever is always:

37% Answer Correctly

less than one

equal to one

not equal to one

greater than 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

Concurrent forces:

55% Answer Correctly

act along the same line of action

act in a common plane

pass through a common point

act in a common dimension
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.