ASVAB Mechanical Comprehension Practice Test 520169 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.62
Score	0%	52%

Review

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

70% Answer Correctly

	third-class lever
	first-class lever
	second-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 of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its speed
	its mass
	its weight
	its direction

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

3 What is the power output of a 2 hp engine that's 95% efficient?

40% Answer Correctly

	190 \( \frac{ft⋅lb}{s} \)
	2090 \( \frac{ft⋅lb}{s} \)
	348.3 \( \frac{ft⋅lb}{s} \)
	1045 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 2 hp x 550 \( \frac{ft⋅lb}{s} \) = 1100 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{95 \times 1100 \frac{ft⋅lb}{s}}{100} \) \( = \frac{104500 \frac{ft⋅lb}{s}}{100} \) = 1045 \( \frac{ft⋅lb}{s} \)

4 If the radius of the axle is 5 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	0
	2
	1
	5

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.

Gear ratio indicates which of the following about two connected gears?

59% Answer Correctly

	efficiency
	mechanical advantage
	work done
	power conversion

Solution

The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.