ASVAB Mechanical Comprehension Practice Test 975917 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.99
Score	0%	60%

Review

Concurrent forces:

55% Answer Correctly

	act along the same line of action
	act in a common dimension
	pass through a common point
	act in a common plane

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

Connected gears of different numbers of teeth are used together to change which of the following charasteristics of the input force?

65% Answer Correctly

	rotational direction
	force
	energy
	torque

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.

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

61% Answer Correctly

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

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).

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

52% Answer Correctly

	first
	third
	all of these
	second

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.

5 A = 8 ft., the green box weighs 15 lbs., and the blue box weighs 25 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	4.8 ft.
	1 ft.
	1.2 ft.
	1.6 ft.

Solution

In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

f_Ad_A = f_Bd_B

For this problem, the equation becomes:

15 lbs. x 8 ft. = 25 lbs. x d_B

d_B = \( \frac{15 \times 8 ft⋅lb}{25 lbs.} \) = \( \frac{120 ft⋅lb}{25 lbs.} \) = 4.8 ft.