ASVAB Mechanical Comprehension Practice Test 348341 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.69
Score	0%	54%

Review

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

59% Answer Correctly

	efficiency
	work done
	power conversion
	mechanical advantage

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.

2 If the handles of a wheelbarrow are 1.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 160 lbs. load concentrated at a point 0.5 ft. from the axle?

52% Answer Correctly

	0
	98.2
	53.3
	-5.6

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. In this problem we're looking for effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{160 \times 0.5}{1.5} \)
\( F_e = \frac{80.0}{1.5} \)
\( F_e = 53.3 \)

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

73% Answer Correctly

	gear systems
	torque
	air pressure
	liquids

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).

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	third
	first
	none of these, all levers offer mechanical advantage
	second

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.

5 If the radius of the axle is 3 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?

36% Answer Correctly

	-5
	5
	2
	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.