ASVAB Mechanical Comprehension Practice Test 506176 Results

Your Results Global Average
Questions 5 5
Correct 0 2.97
Score 0% 59%

Review

1

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

opposite to

parallel to

perpendicular to

along
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

2

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

kinetic friction

dynamic friction

static friction

gravitational friction
Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

3

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

power conversion

work done

mechanical advantage

efficiency
Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear.  For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.

4

Which of the following is the formula for torque?

61% Answer Correctly

τ = r/F

τ = rF

τ = F/r

τ = F/r2
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).

5 If A = 8 ft., B = 2 ft., C = 5 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
50 lbs.
25 lbs.
5 lbs.
12.5 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 8 ft. = 55 lbs. x 2 ft. + fC x 5 ft.

360 ft. lbs. = 110 ft. lbs. + fC x 5 ft.

fC = \( \frac{360 ft. lbs. - 110 ft. lbs.}{5 ft.} \) = \( \frac{250 ft. lbs.}{5 ft.} \) = 50 lbs.