ASVAB Mechanical Comprehension Practice Test 301629 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.03
Score	0%	61%

Review

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

59% Answer Correctly

	if the coefficient of friction is greater than one
	when an attempt is made to move the box
	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).

2 A = 5 ft., the green box weighs 50 lbs., and the blue box weighs 60 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	2.08 ft.
	4.17 ft.
	8.33 ft.
	1.39 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

50 lbs. x 5 ft. = 60 lbs. x d_B

d_B = \( \frac{50 \times 5 ft⋅lb}{60 lbs.} \) = \( \frac{250 ft⋅lb}{60 lbs.} \) = 4.17 ft.

What's the first gear in a gear train called?

57% Answer Correctly

	driven gear
	idler gear
	input gear
	driver gear

Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

	second-class lever
	third-class lever
	first-class lever
	inclined plane

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

Which class of lever is used to increase force on an object in the same direction as the force is applied?

53% Answer Correctly

	second
	all of these
	third
	first

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.