ASVAB Mechanical Comprehension Practice Test 416730 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.55
Score	0%	51%

Review

1 If the radius of the axle is 5 and the radius of the wheel is 8, what is the mechanical advantage of this wheel and axle configuration?

41% Answer Correctly

	0.63
	1.6
	5
	8

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 5 and the output radius (where the resistance is being applied) is 8 for a mechanical advantage of \( \frac{5}{8} \) = 0.63

What is work?

60% Answer Correctly

	The potential for exertion
	The movement of an object by a force
	Force per unit time
	Force per unit distance

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

3 The radius of the axle is 3, the radius of the wheel is 4, and the blue box weighs 45 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	33.83 lbs.
	4.33 lbs.
	3.99 lbs.
	3 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 4 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{4}{3} \) = 1.33

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{45 lbs.}{1.33} \) = 33.83 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

	increase, increase
	decrease, decrease
	increase, decrease
	decrease, 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.

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

	the mechanical advantage of the lever
	the distance traveled by the load
	the speed of the load
	the force applied to the load

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.