ASVAB Mechanical Comprehension Practice Test 556960 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.02
Score	0%	60%

Review

1 If the handles of a wheelbarrow are 2.0 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 140 lbs. load concentrated at a point 0.5 ft. from the axle?

52% Answer Correctly

	560
	280
	35
	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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{140 \times 0.5}{2.0} \)
\( F_e = \frac{70.0}{2.0} \)
\( F_e = 35 \)

2 A mass of air has a pressure of 12.0 psi and a volume of 60 ft.³. If the air is compressed to a new volume of 55 ft.³, what is the new pressure?

56% Answer Correctly

	26.2 psi
	6.5 psi
	13.1 psi
	15.1 psi

Solution

According to Boyle's Law, pressure and volume are inversely proportional:

\( \frac{P_1}{P_2} \) = \( \frac{V_2}{V_1} \)

In this problem, V₂ = 55 ft.³, V₁ = 60 ft.³ and P₁ = 12.0 psi. Solving for P₂:

P₂ = \( \frac{P_1}{\frac{V_2}{V_1}} \) = \( \frac{12.0 psi}{\frac{55 ft.^3}{60 ft.^3}} \) = 13.1 psi

3 The green box weighs 5 lbs. and a 45 lbs. weight is placed 7 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

	15.75 ft.
	252 ft.
	1 ft.
	63 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 = \( \frac{R_bd_b}{R_a} \) = \( \frac{45 lbs. \times 7 ft.}{5 lbs.} \) = \( \frac{315 ft⋅lb}{5 lbs.} \) = 63 ft.

4 If the green arrow in this diagram represents 180 ft⋅lb of work, how far will the box move if it weighs 90 pounds?

72% Answer Correctly

	8 ft.
	180 ft.
	45 ft.
	2 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 180 ft⋅lb and the resistance force is 90 lbs. and we need to calculate the resistance distance:

W_in = F_resistance x d_resistance
180 ft⋅lb = 90 lbs. x d_resistance
d_resistance = \( \frac{180ft⋅lb}{90 lbs.} \) = 2 ft.

When it comes to force, mass and acceleration have what kind of relationship?

66% Answer Correctly

	logarithmic
	linear
	inverse
	exponential

Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.