ASVAB Mechanical Comprehension Practice Test 549875 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.13
Score	0%	63%

Review

A a seesaw / teeter-totter is an example of which of the following?

69% Answer Correctly

	third-class lever
	inclined plane
	second-class lever
	first-class lever

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.

A watt is the unit for which of the following?

71% Answer Correctly

	power
	mechanical advantage
	energy
	work

Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

3 What is the power output of a 5 hp engine that's 45% efficient?

40% Answer Correctly

	309.4 \( \frac{ft⋅lb}{s} \)
	3712.5 \( \frac{ft⋅lb}{s} \)
	1237.5 \( \frac{ft⋅lb}{s} \)
	9 \( \frac{ft⋅lb}{s} \)

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 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{45 \times 2750 \frac{ft⋅lb}{s}}{100} \) \( = \frac{123750 \frac{ft⋅lb}{s}}{100} \) = 1237.5 \( \frac{ft⋅lb}{s} \)

What is the first step to solving a problem where multiple forces are acting on an object?

61% Answer Correctly

	calculate the total force
	calculate potential energy
	calculate kinetic energy
	calculate the net force

Solution

In mechanics, multiple forces are often acting on a particular object and, taken together, produce the net force acting on that object. Like force, net force is a vector quantity in that it has magnitude and direction.

The force exerted on an object due to gravity is called:

69% Answer Correctly

	weight
	mass
	density
	potential energy

Solution

Mass is an intrinsic property of matter and does not vary. Weight is the force exerted on the mass of an object due to gravity and a specific case of Newton's Second Law of Motion. Replace force with weight and acceleration with acceleration due to gravity on Earth (g) and the result is the formula for weight: W = mg or, substituting for g, weight equals mass multiplied by 9.8 m/s².