ASVAB Mechanical Comprehension Practice Test 283880 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.76
Score	0%	55%

Review

1 A 380 lb. barrel is rolled up a 17 ft. ramp to a platform that's 2 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	47.7 lbs.
	22.4 lbs.
	44.7 lbs.
	89.4 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 17 ft. = 380 lbs. x 2 ft.
F_e = \( \frac{760 ft⋅lb}{17 ft.} \) = 44.7 lbs.

The mass of an object correlates to the size of the object but ultimately depends on:

67% Answer Correctly

	the object's weight
	the object's density
	gravity
	the object's potential energy

Solution

Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.

Which of the following is the formula for gravitational potential energy?

62% Answer Correctly

	\(PE = mg^2h\)
	\(PE = { 1 \over 2} mv^2\)
	\(PE = mgh\)
	\(PE = { 1 \over 2} mg^2\)

Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s²).

4 If the force applied at the blue arrow over 7 ft. moves the green box 3.5 ft., what is the mechanical advantage of this lever?

56% Answer Correctly

	4
	2
	-7
	6

Solution

Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:

MA = \( \frac{E_d}{R_d} \)

where E_d is the effort distance and R_d is the resistance distance. For this problem, the equation becomes:

MA = \( \frac{7 ft.}{3.5 ft.} \) = 2

You might be wondering how having an effort distance of 2 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 2 times the resistance distance, the effort force must be \( \frac{1}{2} \) the resistance force. You're trading moving 2 times the distance for only having to use \( \frac{1}{2} \) the force.

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

38% Answer Correctly

	output gear
	driver gear
	driven gear
	idler 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.