ASVAB Mechanical Comprehension Practice Test 716096 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.98
Score	0%	60%

Review

1 If the green box weighs 50 lbs. and 25 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow, how far from the fulcrum would the green box need to be placed to balance the lever?

55% Answer Correctly

	0.83 ft.
	1.25 ft.
	2.5 ft.
	5 ft.

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 d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{25 lbs. \times 5 ft.}{50 lbs.} \) = \( \frac{125 ft⋅lb}{50 lbs.} \) = 2.5 ft.

2 If A = 9 ft., B = 3 ft., C = 7 ft., the green box weighs 30 lbs. and the blue box weighs 50 lbs., what does the orange box have to weigh for this lever to balance?

43% Answer Correctly

	17.14 lbs.
	51.43 lbs.
	4.29 lbs.
	270 lbs.

Solution

In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. 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 + f_Cd_C

For this problem, this equation becomes:

30 lbs. x 9 ft. = 50 lbs. x 3 ft. + f_C x 7 ft.

270 ft. lbs. = 150 ft. lbs. + f_C x 7 ft.

f_C = \( \frac{270 ft. lbs. - 150 ft. lbs.}{7 ft.} \) = \( \frac{120 ft. lbs.}{7 ft.} \) = 17.14 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

	acceleration
	kinetic energy
	total mechanical energy
	potential 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.

4 What is the mechanical advantage of this inclined plane if the length of the ramp is 10 ft. and the height of the green box is 5 ft.?

82% Answer Correctly

	2.2
	10
	0
	2

Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{10 ft.}{5 ft.} \) = 2

Collinear forces:

72% Answer Correctly

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

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.