ASVAB Mechanical Comprehension Practice Test 311125 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.20
Score	0%	64%

Review

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?

55% Answer Correctly

	increase applied force
	decrease applied force
	increase torque
	decrease torque

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).

Collinear forces:

73% Answer Correctly

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

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.

Assuming force applied remains constant, which of the following will result in more work being done?

53% Answer Correctly

	moving the object with more speed
	increasing the coefficient of friction
	moving the object farther
	moving the object with more acceleration

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.

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

62% Answer Correctly

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

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).

5 If you have a gear train with two gears, the first with 28 teeth and the second with 4 teeth, how many revolutions does the second gear make for each revolution of the first gear?

78% Answer Correctly

	7
	6.3
	14
	2.3

Solution

The gear ratio (V_r) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{28}{4} \) = 7