ASVAB Mechanical Comprehension Practice Test 950073 Results

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

Review

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

	conservation of mechanical energy
	Pascal's law
	work-energy theorem
	mechanical advantage

Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.

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

61% Answer Correctly

	decrease, increase
	increase, decrease
	decrease, decrease
	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.

Collinear forces:

72% Answer Correctly

	act in a common plane
	pass through a common point
	act along the same line of action
	are unrelated to each other

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.

Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?

54% Answer Correctly

	decrease applied force
	decrease torque
	increase torque
	increase applied force

Solution

Torque measures force applied during rotation: τ = rF. Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).

5 If the green arrow in this diagram represents 400 ft⋅lb of work, how far will the box move if it weighs 100 pounds?

72% Answer Correctly

	4 ft.
	16 ft.
	1 ft.
	25 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 400 ft⋅lb and the resistance force is 100 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
400 ft⋅lb = 100 lbs. x d_resistance
d_resistance = \( \frac{400ft⋅lb}{100 lbs.} \) = 4 ft.