ASVAB Mechanical Comprehension Practice Test 480887 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.60
Score	0%	52%

Review

The advantage of using a third-class lever is that it increases:

37% Answer Correctly

	the mechanical advantage of the lever
	the force applied to the load
	the distance traveled by the load
	the speed of the load

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

2 If 10 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 1 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

62% Answer Correctly

	2 lbs.
	50 lbs.
	100 lbs.
	200 lbs.

Solution

To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

Solving for R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{10 lbs. \times 5 ft.}{1 ft.} \) = \( \frac{50 ft⋅lb}{1 ft.} \) = 50 lbs.

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

	total mechanical energy
	acceleration
	potential energy
	kinetic energy

Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

What type of load is sudden and for a relatively short duration?

69% Answer Correctly

	impact load
	non-uniformly distributed load
	concentrated load
	dynamic load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

5 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle and the load is concentrated at a point 1.0 ft. from the axle, how many pounds of load will a 200 lbs. force lift?

47% Answer Correctly

	200
	133.9
	100
	400

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. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{200 \times 2.0}{1.0} \)
\( F_r = \frac{400.0}{1.0} \)
\( F_r = 400 \)