ASVAB Mechanical Comprehension Practice Test 484332 Results

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

Review

1 If A = 12 ft., B = 1 ft., C = 7 ft., the green box weighs 50 lbs. and the blue box weighs 55 lbs., what does the orange box have to weigh for this lever to balance?
43% Answer Correctly
77.86 lbs.
233.57 lbs.
4 lbs.
25.95 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 12 ft. = 55 lbs. x 1 ft. + fC x 7 ft.

600 ft. lbs. = 55 ft. lbs. + fC x 7 ft.

fC = \( \frac{600 ft. lbs. - 55 ft. lbs.}{7 ft.} \) = \( \frac{545 ft. lbs.}{7 ft.} \) = 77.86 lbs.

2

A box is resting on a smooth floor. Static friction is present:

59% Answer Correctly

when an attempt is made to move the box

if the coefficient of friction is greater than one

at all times

only if normal force is present
Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).

3

Collinear forces:

72% Answer Correctly

pass through a common point

are unrelated to each other

act in a common plane

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.

4

The mechanical advantage of a wheel and axle is equal to the:

61% Answer Correctly

difference in the diameters of the wheels

length of the axle

ratio of the diameters of the wheels

difference in the lengths of the axles
Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

5

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

45 lbs

810 lbs

0.83 lbs

90 lbs
Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: Fede = Frdr. Plugging in the variables from this problem yields:

Fe x 3 ft. = 270 lbs x 0.5 ft
Fe = 135 ft-lb. / 3 ft 
Fe = 45 lbs