ASVAB Mechanical Comprehension Practice Test 314287 Results

Your Results Global Average
Questions 5 5
Correct 0 3.50
Score 0% 70%

Review

1

A ramp is an example of which kind of simple machine?

84% Answer Correctly

first-class lever

inclined plane

none of these

wedge
Solution

An inclined plane is a simple machine that reduces the force needed to raise an object to a certain height. Work equals force x distance and, by increasing the distance that the object travels, an inclined plane reduces the force necessary to raise it to a particular height. In this case, the mechanical advantage is to make the task easier. An example of an inclined plane is a ramp.

2

Which of the following is not true of a  first-class lever?

51% Answer Correctly

changes the direction of force

increases distance

increases force

decreases distance
Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

3

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

block and tackle

wheel and axle

first-class lever

fixed pulley
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.

4

Which of these is the formula for force?

76% Answer Correctly

F = m/a

F = am2

F = a/m

F = ma
Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

5 If A = 9 ft., B = 3 ft., C = 6 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?
44% Answer Correctly
47.5 lbs.
16 lbs.
190 lbs.
15.83 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. = 55 lbs. x 3 ft. + fC x 6 ft.

450 ft. lbs. = 165 ft. lbs. + fC x 6 ft.

fC = \( \frac{450 ft. lbs. - 165 ft. lbs.}{6 ft.} \) = \( \frac{285 ft. lbs.}{6 ft.} \) = 47.5 lbs.