ASVAB Mechanical Comprehension Practice Test 150032 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.23
Score	0%	65%

Review

Power is the rate at which:

62% Answer Correctly

	work is done
	potential energy is converted into kinetic energy
	friction is overcome
	input force is transferred to output force

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.

2 If the green arrow in this diagram represents 630 ft⋅lb of work, how far will the box move if it weighs 210 pounds?

73% Answer Correctly

	70 ft.
	52 ft.
	12 ft.
	3 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 630 ft⋅lb and the resistance force is 210 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
630 ft⋅lb = 210 lbs. x d_resistance
d_resistance = \( \frac{630ft⋅lb}{210 lbs.} \) = 3 ft.

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	force or speed
	speed or power
	force or distance
	power or distance

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

A a seesaw / teeter-totter is an example of which of the following?

70% Answer Correctly

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

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

Hydraulics is the transmission of force through the use of which of the following?

74% Answer Correctly

	air pressure
	torque
	liquids
	gear systems

Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).