ASVAB Mechanical Comprehension Practice Test 244540 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.09
Score	0%	62%

Review

A watt is the unit for which of the following?

71% Answer Correctly

	energy
	power
	mechanical advantage
	work

Solution

Power is the rate at which work is done, P = w/t, or work per unit time. The watt (W) is the unit for power and is equal to 1 joule (or newton-meter) per second. Horsepower (hp) is another familiar unit of power used primarily for rating internal combustion engines. 1 hp equals 746 watts.

2 If input effort is 200 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 8?

79% Answer Correctly

	400ft⋅lb
	6400ft⋅lb
	0ft⋅lb
	1600 ft⋅lb

Solution

Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 8 will multiply an input effort of 200 ft⋅lb by 8 to produce an output effort of 1600 ft⋅lb.

3 The radius of the axle is 5, the radius of the wheel is 8, and the blue box weighs 35 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	8 lbs.
	6.6 lbs.
	40 lbs.
	21.88 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 8 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{8}{5} \) = 1.6

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{35 lbs.}{1.6} \) = 21.88 lbs.

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

53% Answer Correctly

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

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.

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).