ASVAB Mechanical Comprehension Practice Test 590925 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.18
Score	0%	64%

Review

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	first
	third
	none of these, all levers offer mechanical advantage
	second

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

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

61% Answer Correctly

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

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).

3 What is the mechanical advantage of this inclined plane if the length of the ramp is 4 ft. and the height of the green box is 2 ft.?

82% Answer Correctly

	5
	0
	2
	6

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{4 ft.}{2 ft.} \) = 2

4 How much work can a 6 hp engine do in 7 seconds?

52% Answer Correctly

	12 ft⋅lb
	24 ft⋅lb
	1 ft⋅lb
	23100 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 6 hp \times 550 \frac{ft⋅lb}{s} \times 7s = 23100 ft⋅lb \)

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

79% Answer Correctly

	2
	1
	0
	4

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.