ASVAB Mechanical Comprehension Practice Test 874144 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.17
Score	0%	63%

Review

1 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

	750ft⋅lb
	1500 ft⋅lb
	375ft⋅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.

Which class of lever is used to increase force on an object in the same direction as the force is applied?

53% Answer Correctly

	third
	second
	all of these
	first

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

	dynamic load
	static uniformly distributed load
	impact load
	non-uniformly distributed load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

4 If the green arrow in this diagram represents 760 ft⋅lb of work, how far will the box move if it weighs 190 pounds?

72% Answer Correctly

	4 ft.
	16 ft.
	760 ft.
	95 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 760 ft⋅lb and the resistance force is 190 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
760 ft⋅lb = 190 lbs. x d_resistance
d_resistance = \( \frac{760ft⋅lb}{190 lbs.} \) = 4 ft.

For any given surface, the coefficient of static friction is ___________ the coefficient of kinetic friction.

54% Answer Correctly

	lower than
	opposite
	higher than
	equal to

Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).