ASVAB Mechanical Comprehension Practice Test 363470 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.08
Score	0%	62%

Review

Power is the rate at which:

62% Answer Correctly

	potential energy is converted into kinetic energy
	input force is transferred to output force
	work is done
	friction is overcome

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 100 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 8?

79% Answer Correctly

	200ft⋅lb
	0ft⋅lb
	3200ft⋅lb
	800 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 100 ft⋅lb by 8 to produce an output effort of 800 ft⋅lb.

A fixed pulley is useful for which of the following?

53% Answer Correctly

	multiplying the input force
	multiplying the input distance
	changing the direction of the input force
	changing the direction of the output force

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	45 lbs
	810 lbs
	0.83 lbs
	90 lbs

Solution

This problem describes a second-class lever and, for a second class lever, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance: F_ed_e = F_rd_r. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

Which of the following statements about drag is false?

58% Answer Correctly

	drag occurs during movement through a fluid
	the amount of drag depends on the speed of an object
	slower objects experience more drag than faster objects
	the amount of drag depends on the shape of an object

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.