ASVAB Mechanical Comprehension Practice Test 868823 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.11
Score	0%	62%

Review

For any given surface, the coefficient of static friction is ___________ the coefficient of kinetic friction.

54% Answer Correctly

	lower than
	equal to
	opposite
	higher than

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).

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

	density, volume
	pressure, density
	volume, mass
	pressure, volume

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".

3 If the green arrow in this diagram represents 140 ft⋅lb of work, how far will the box move if it weighs 70 pounds?

72% Answer Correctly

	8 ft.
	2 ft.
	17 ft.
	4 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 140 ft⋅lb and the resistance force is 70 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
140 ft⋅lb = 70 lbs. x d_resistance
d_resistance = \( \frac{140ft⋅lb}{70 lbs.} \) = 2 ft.

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

66% Answer Correctly

	force
	rotational direction
	energy
	torque

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	decrease the length of the lever
	move the object being lifted closer to the fulcrum
	move the object being lifted farther away from the fulcrum
	move the fulcrum between the force and the object being lifted

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.