ASVAB Mechanical Comprehension Practice Test 840754 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.07
Score	0%	61%

Review

1 If the green box weighs 40 lbs. and 60 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

	15 ft.
	1.88 ft.
	7.5 ft.
	2.5 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 = \( \frac{R_bd_b}{R_a} \) = \( \frac{60 lbs. \times 5 ft.}{40 lbs.} \) = \( \frac{300 ft⋅lb}{40 lbs.} \) = 7.5 ft.

An object's resistance to changes in direction is known as:

81% Answer Correctly

	inertia
	weight
	kinetic energy
	mass

Solution

The more mass a substance has the more force is required to move it or to change its direction. This resistance to changes in direction is known as inertia.

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	position of the fulcrum
	output force
	output distance
	input force

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

4 How much work can a 8 hp engine do in 3 seconds?

52% Answer Correctly

	0 ft⋅lb
	13200 ft⋅lb
	32 ft⋅lb
	16 ft⋅lb

Solution

Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 8 hp \times 550 \frac{ft⋅lb}{s} \times 3s = 13200 ft⋅lb \)

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	force or distance
	power or distance
	speed or power
	force or speed

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.