ASVAB Mechanical Comprehension Practice Test 979393 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.85
Score	0%	57%

Review

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

	along
	perpendicular to
	opposite to
	parallel to

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.

2 A = 6 ft., the green box weighs 30 lbs., and the blue box weighs 35 lbs. What does distance B need to be for this lever to balance?

65% Answer Correctly

	1.71 ft.
	210 ft.
	5.14 ft.
	15.43 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:

30 lbs. x 6 ft. = 35 lbs. x d_B

d_B = \( \frac{30 \times 6 ft⋅lb}{35 lbs.} \) = \( \frac{180 ft⋅lb}{35 lbs.} \) = 5.14 ft.

3 If the force applied at the blue arrow over 9 ft. moves the green box 4.5 ft., what is the mechanical advantage of this lever?

56% Answer Correctly

	1.8
	6
	2
	3

Solution

Mechanical advantage (MA) can be calculated knowing only the distance the effort (blue arrow) moves and the distance the resistance (green box) moves. The equation is:

MA = \( \frac{E_d}{R_d} \)

where E_d is the effort distance and R_d is the resistance distance. For this problem, the equation becomes:

MA = \( \frac{9 ft.}{4.5 ft.} \) = 2

You might be wondering how having an effort distance of 2 times the resistance distance is an advantage. Remember the principle of moments. For a lever in equilibrium the effort torque equals the resistance torque. Because torque is force x distance, if the effort distance is 2 times the resistance distance, the effort force must be \( \frac{1}{2} \) the resistance force. You're trading moving 2 times the distance for only having to use \( \frac{1}{2} \) the force.

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

	increase applied force
	decrease applied force
	decrease torque
	increase 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).

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

53% Answer Correctly

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