ASVAB Mechanical Comprehension Practice Test 346521 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.54
Score	0%	51%

Review

Which class of lever offers no mechanical advantage?

45% Answer Correctly

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

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.

What is work?

60% Answer Correctly

	The movement of an object by a force
	Force per unit time
	The potential for exertion
	Force per unit distance

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

A screw is most like which of the following other simple machines?

50% Answer Correctly

	inclined plane
	first-class lever
	block and tackle
	wheel and axle

Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

4 What is the power output of a 5 hp engine that's 65% efficient?

40% Answer Correctly

	7150 \( \frac{ft⋅lb}{s} \)
	595.8 \( \frac{ft⋅lb}{s} \)
	325 \( \frac{ft⋅lb}{s} \)
	1787.5 \( \frac{ft⋅lb}{s} \)

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 5 hp x 550 \( \frac{ft⋅lb}{s} \) = 2750 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{65 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{178750 \frac{ft⋅lb}{s}}{100} \) = 1787.5 \( \frac{ft⋅lb}{s} \)

Which of the following statements about drag is false?

58% Answer Correctly

	the amount of drag depends on the speed of an object
	the amount of drag depends on the shape of an object
	drag occurs during movement through a fluid
	slower objects experience more drag than faster objects

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.