ASVAB Mechanical Comprehension Practice Test 479636 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.25
Score	0%	65%

Review

1 If this lever is in equilibrium with an effort force of 12.86 ft. lb. at the blue arrow and a resistance force of 9 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	0.35
	0.7
	1.4
	2.1

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{9 ft.}{12.86 ft.} \) = 0.7

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.7 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.

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

61% Answer Correctly

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

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.

3 If A = 5 ft. and the green box weighs 40 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	8 ft⋅lb
	200 ft⋅lb
	800 ft⋅lb
	100 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 40 ft. x 5 lbs. = 200 ft⋅lb

One Horsepower (hp) is equal to how many watts?

76% Answer Correctly

	1
	746
	9.8
	1492

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.

Which of these is the formula for kinetic energy?

67% Answer Correctly

	\(KE = mgh\)
	\(KE = {m \over v^2 }\)
	\(KE = {1 \over 2}mv^2\)
	\(KE = {1 \over 2}mh^2\)

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.