ASVAB Mechanical Comprehension Practice Test 764348 Results

Your Results Global Average
Questions 5 5
Correct 0 3.15
Score 0% 63%

Review

1

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

84% Answer Correctly

none of these

inclined plane

first-class lever

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

A fixed pulley is useful for which of the following?

53% Answer Correctly

multiplying the input force

multiplying the input distance

changing the direction of the output force

changing the direction of the input force


Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.


3

Power is the rate at which:

62% Answer Correctly

input force is transferred to output force

potential energy is converted into kinetic energy

friction is overcome

work is done


Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.


4

A shovel is an example of which class of lever?

56% Answer Correctly

a shovel is not a lever

third

first

second


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.


5

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

59% Answer Correctly

if the coefficient of friction is greater than one

only if normal force is present

at all times

when an attempt is made to move the box


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).