ASVAB Mechanical Comprehension Practice Test 495471 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.34
Score	0%	67%

Review

1 If a 35 lbs. weight is placed 1 ft. from the fulcrum at the blue arrow and the green box is 6 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	5.83 lbs.
	35 lbs.
	11.67 lbs.
	23.33 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 = \( \frac{R_bd_b}{d_a} \) = \( \frac{35 lbs. \times 1 ft.}{6 ft.} \) = \( \frac{35 ft⋅lb}{6 ft.} \) = 5.83 lbs.

For a hydraulic system, pressure applied to the input of the system will increase the pressure in which parts of the system?

58% Answer Correctly

	all of these are correct
	everywhere in the system
	the portions of the system at an altitude below the input
	the portions of the system at an altitude above the input

Solution

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.

3 If input effort is 200 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 7?

79% Answer Correctly

	2800ft⋅lb
	0ft⋅lb
	1400 ft⋅lb
	350ft⋅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 7 will multiply an input effort of 200 ft⋅lb by 7 to produce an output effort of 1400 ft⋅lb.

Two or more pulleys used together are called:

71% Answer Correctly

	wheel and axle
	third-class lever
	block and tackle
	gears

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

65% Answer Correctly

	energy
	torque
	rotational direction
	force

Solution

Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.