ASVAB Mechanical Comprehension Practice Test 556981 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.35
Score	0%	67%

Review

A block and tackle with four pulleys would have a mechanical advantage of:

79% Answer Correctly

	1
	0
	2
	4

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

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.

3 If a 75 lbs. weight is placed 9 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	21.09 lbs.
	84.38 lbs.
	42.19 lbs.
	8 lbs.

Solution

To balance this lever the torques on each side of the fulcrum 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 left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

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

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{75 lbs. \times 9 ft.}{8 ft.} \) = \( \frac{675 ft⋅lb}{8 ft.} \) = 84.38 lbs.

4 What is the power output of a 7 hp engine that's 75% efficient?

40% Answer Correctly

	962.5 \( \frac{ft⋅lb}{s} \)
	2887.5 \( \frac{ft⋅lb}{s} \)
	8662.5 \( \frac{ft⋅lb}{s} \)
	11550 \( \frac{ft⋅lb}{s} \)

Solution

\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), P_i becomes 7 hp x 550 \( \frac{ft⋅lb}{s} \) = 3850 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{75 \times 3850 \frac{ft⋅lb}{s}}{100} \) \( = \frac{288750 \frac{ft⋅lb}{s}}{100} \) = 2887.5 \( \frac{ft⋅lb}{s} \)

Potential energy is energy that has the potential to be converted into what?

80% Answer Correctly

	kinetic energy
	power
	heat
	work

Solution

Potential energy is the energy of an object by virtue of its position relative to other objects. It is energy that has the potential to be converted into kinetic energy.