ASVAB Mechanical Comprehension Practice Test 48319 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.40
Score	0%	68%

Review

The steering wheel of a car is an example of which type of simple machine?

89% Answer Correctly

	block and tackle
	first-class lever
	wheel and axle
	fixed pulley

Solution

A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.

2 What is the efficiency of a machine has work input of 205 ft⋅lb and work output of 92 ft⋅lb?

67% Answer Correctly

	90%
	22%
	45%
	55%

Solution

Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{92 ft⋅lb}{205 ft⋅lb} \times 100 \) \( = 45% \) %

The standard unit of energy is the:

73% Answer Correctly

	Horsepower
	Joule
	Watt
	Volt

Solution

The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).

A shovel is an example of which class of lever?

56% Answer Correctly

	a shovel is not a lever
	second
	third
	first

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.

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 farther away from the fulcrum
	move the object being lifted closer to 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.