ASVAB Mechanical Comprehension Practice Test 606033 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.89
Score	0%	58%

Review

1 If the green arrow in this diagram represents 510 ft⋅lb of work, how far will the box move if it weighs 170 pounds?

73% Answer Correctly

	3 ft.
	0 ft.
	340 ft.
	680 ft.

Solution

The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

W_in = W_out
F_effort x d_effort = F_resistance x d_resistance

In this problem, the effort work is 510 ft⋅lb and the resistance force is 170 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
510 ft⋅lb = 170 lbs. x d_resistance
d_resistance = \( \frac{510ft⋅lb}{170 lbs.} \) = 3 ft.

2 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 100 lbs. force lift?

47% Answer Correctly

	512.1
	130.2
	200
	0

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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{100 \times 2.0}{1.0} \)
\( F_r = \frac{200.0}{1.0} \)
\( F_r = 200 \)

3 The green box weighs 30 lbs. and a 30 lbs. weight is placed 1 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?

57% Answer Correctly

	30 ft.
	2 ft.
	0.5 ft.
	1 ft.

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

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{30 lbs. \times 1 ft.}{30 lbs.} \) = \( \frac{30 ft⋅lb}{30 lbs.} \) = 1 ft.

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its weight
	its direction
	its speed
	its mass

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

Specific gravity is a comparison of the density of an object with the density of:

57% Answer Correctly

	oil
	water
	carbon
	air

Solution

Specific gravity is the ratio of the density of equal volumes of a substance and water and is measured by a hyrdometer.