ASVAB Mechanical Comprehension Practice Test 286164 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.95
Score	0%	59%

Review

Which of the following is not true of a first-class lever?

51% Answer Correctly

	decreases distance
	changes the direction of force
	increases distance
	increases force

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.

The principle of moments defines equilibrium in terms of:

53% Answer Correctly

	speed
	power
	torque
	energy

Solution

According to the principle of moments, you can maintain equilibrium if the moments (forces) tending to clockwise rotation are equal to the moments tending to counterclockwise rotation. Another name for these moments of force is torque.

3 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 140 lbs. load concentrated at a point 0.5 ft. from the axle?

52% Answer Correctly

	94.2
	None of these is correct
	69.4
	70

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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{140 \times 0.5}{1.0} \)
\( F_e = \frac{70.0}{1.0} \)
\( F_e = 70 \)

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

73% Answer Correctly

	air pressure
	gear systems
	liquids
	torque

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).

According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?

63% Answer Correctly

	pressure, density
	volume, mass
	pressure, volume
	density, volume

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".