ASVAB Mechanical Comprehension Practice Test 624036 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.94
Score	0%	59%

Review

1 If the radius of the axle is 7 and the radius of the wheel is 12, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	1
	12
	-5
	1

Solution

The mechanical advantage of a wheel and axle lies in the difference in radius between the inner (axle) wheel and the outer wheel. But, this mechanical advantage is only realized when the input effort and load are applied to different wheels. Applying both input effort and load to the same wheel results in a mechanical advantage of 1.

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

69% Answer Correctly

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

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.

Power is the rate at which:

62% Answer Correctly

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

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.

Friction between two or more solid objects that are not moving relative to each other is called:

73% Answer Correctly

	static friction
	kinetic friction
	gravitational friction
	dynamic friction

Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.

5 How much work can a 3 hp engine do in 9 seconds?

52% Answer Correctly

	3 ft⋅lb
	14850 ft⋅lb
	0 ft⋅lb
	12 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 3 hp \times 550 \frac{ft⋅lb}{s} \times 9s = 14850 ft⋅lb \)