ASVAB Mechanical Comprehension Practice Test 560687 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.64
Score	0%	53%

Review

When all forces acting on a system cancel each other out, this is called:

81% Answer Correctly

	potential energy
	stasis
	rest
	equilibrium

Solution

When a system is stable or balanced (equilibrium) all forces acting on the system cancel each other out. In the case of torque, equilibrium means that the sum of the anticlockwise moments about a center of rotation equal the sum of the clockwise moments.

2 What is the power output of a 1 hp engine that's 85% efficient?

40% Answer Correctly

	935 \( \frac{ft⋅lb}{s} \)
	233.8 \( \frac{ft⋅lb}{s} \)
	467.5 \( \frac{ft⋅lb}{s} \)
	155.8 \( \frac{ft⋅lb}{s} \)

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 1 hp x 550 \( \frac{ft⋅lb}{s} \) = 550 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{85 \times 550 \frac{ft⋅lb}{s}}{100} \) \( = \frac{46750 \frac{ft⋅lb}{s}}{100} \) = 467.5 \( \frac{ft⋅lb}{s} \)

What's the first gear in a gear train called?

57% Answer Correctly

	idler gear
	driver gear
	driven gear
	input gear

Solution

A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.

The mechanical advantage of a third class lever is always:

37% Answer Correctly

	less than one
	not equal to one
	greater than one
	equal to one

Solution

A third class lever is designed to multiply distance and speed at the expense of effort force. Because the effort force is greater than the resistance, the mechanical advantage of a third class lever is always less than one.

An example of a third class lever is a broom. The fulcrum is at your hand on the end of the broom, the effort force is your other hand in the middle, and the resistance is at the bottom bristles. The effort force of your hand in the middle multiplies the distance and speed of the bristles at the bottom but at the expense of producing a brushing force that's less than the force you're applying with your hand.

Which class of lever offers no mechanical advantage?

45% Answer Correctly

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