ASVAB Mechanical Comprehension Practice Test 422912 Results

Your Results Global Average
Questions 5 5
Correct 0 3.35
Score 0% 67%

Review

1

Which class of lever offers no mechanical advantage?

45% Answer Correctly

none of these, all levers offer mechanical advantage

first

second

third
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

Two or more pulleys used together are called:

71% Answer Correctly

gears

third-class lever

block and tackle

wheel and axle
Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement.  So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

3

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

59% Answer Correctly

only if normal force is present

if the coefficient of friction is greater than one

when an attempt is made to move the box

at all times
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).

4 80 lbs. of effort is used by a machine to lift a 720 lbs. box. What is the mechanical advantage of the machine?
84% Answer Correctly
18
10.5
10
9
Solution

Mechanical advantage is resistance force divided by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{720 lbs.}{80 lbs.} \) = 9

5

The force required to initally get an object moving is __________ the force required to keep it moving. 

76% Answer Correctly

lower than

opposite

higher than

the same as
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).