ASVAB Mechanical Comprehension Practice Test 415112 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.55
Score	0%	71%

Review

1 If input effort is 100 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 8?

79% Answer Correctly

	1600ft⋅lb
	800 ft⋅lb
	3200ft⋅lb
	0ft⋅lb

Solution

Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 8 will multiply an input effort of 100 ft⋅lb by 8 to produce an output effort of 800 ft⋅lb.

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

76% Answer Correctly

	1492
	746
	9.8
	1

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.

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

	do the work in 3 minutes
	do 100 ft. lb. of work in 4 minutes 12 seconds
	do 25 ft. lb. of work in 2 minutes 5 seconds
	do the work in 2 minutes

Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.

4 If a 30 lbs. weight is placed 1 ft. from the fulcrum at the blue arrow and the green box is 2 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	15 lbs.
	45 lbs.
	60 lbs.
	3.75 lbs.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{30 lbs. \times 1 ft.}{2 ft.} \) = \( \frac{30 ft⋅lb}{2 ft.} \) = 15 lbs.

Friction between two or more solid objects that are not moving relative to each other is called:

74% Answer Correctly

	dynamic friction
	kinetic friction
	gravitational friction
	static friction

Solution

Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.