ASVAB Mechanical Comprehension Practice Test 168679 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.68
Score	0%	74%

Review

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	0
	2
	4
	1

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.

2 If you lift a 20 lbs. rock 37 ft. from the ground, how much work have you done?

71% Answer Correctly

	-17 ft⋅lb
	57 ft⋅lb
	740 ft⋅lb
	370 ft⋅lb

Solution

Work is force times distance. In this case, the force is the weight of the rock so:
\( W = F \times d \)
\( W = 20 \times 37 \)
\( W = 740 \)

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

61% Answer Correctly

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

4 If input effort is 300 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 5?

79% Answer Correctly

	1500 ft⋅lb
	6000ft⋅lb
	0ft⋅lb
	3000ft⋅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 5 will multiply an input effort of 300 ft⋅lb by 5 to produce an output effort of 1500 ft⋅lb.

Friction resists movement in a direction __________ to the movement.

81% Answer Correctly

	parallel
	normal
	perpendicular
	opposite

Solution

Friction resists movement. Kinetic (also called sliding or dynamic) friction resists movement in a direction opposite to the movement. Because it opposes movement, kinetic friction will eventually bring an object to a stop. An example is a rock that's sliding across ice.