ASVAB Mechanical Comprehension Practice Test 914285 Results

Your Results Global Average
Questions 5 5
Correct 0 2.79
Score 0% 56%

Review

1

Which class of lever offers no mechanical advantage?

45% Answer Correctly

third

none of these, all levers offer mechanical advantage

second

first
Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

2

When all forces acting on a system cancel each other out, this is called:

80% Answer Correctly

potential energy

stasis

rest

equilibrium
Solution

When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.

3

For a hydraulic system, pressure applied to the input of the system will increase the pressure in which parts of the system?

58% Answer Correctly

everywhere in the system

all of these are correct

the portions of the system at an altitude below the input

the portions of the system at an altitude above the input
Solution

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.

4 If the handles of a wheelbarrow are 0.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 170 lbs. load concentrated at a point 1.0 ft. from the axle?
52% Answer Correctly
195.4
85
340
38.7
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. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{170 \times 1.0}{0.5} \)
\( F_e = \frac{170.0}{0.5} \)
\( F_e = 340 \)
5 If the radius of the axle is 3 and the radius of the wheel is 6, what is the mechanical advantage of this wheel and axle configuration?
41% Answer Correctly
0.5
2.0
6
3
Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 3 and the output radius (where the resistance is being applied) is 6 for a mechanical advantage of \( \frac{3}{6} \) = 0.5