ASVAB Mechanical Comprehension Practice Test 659592 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.25
Score	0%	65%

Review

1 If the green arrow in this diagram represents 1000 ft⋅lb of work, how far will the box move if it weighs 200 pounds?

72% Answer Correctly

	20 ft.
	0 ft.
	40 ft.
	5 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 1000 ft⋅lb and the resistance force is 200 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
1000 ft⋅lb = 200 lbs. x d_resistance
d_resistance = \( \frac{1000ft⋅lb}{200 lbs.} \) = 5 ft.

2 The radius of the axle is 3, the radius of the wheel is 8, and the blue box weighs 80 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	29.96 lbs.
	21.36 lbs.
	24 lbs.
	8 lbs.

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 8 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{8}{3} \) = 2.67

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{80 lbs.}{2.67} \) = 29.96 lbs.

Two gears are connected and the smaller gear drives the larger gear. The speed of rotation will __________ and the torque will __________.

61% Answer Correctly

	decrease, decrease
	increase, decrease
	decrease, increase
	increase, increase

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.

A wedge is most similar to what other type of simple machine?

70% Answer Correctly

	third-class lever
	second-class lever
	inclined plane
	first-class lever

Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

What type of load is sudden and for a relatively short duration?

69% Answer Correctly

	dynamic load
	impact load
	non-uniformly distributed load
	concentrated 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.