ASVAB Mechanical Comprehension Practice Test 35606 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.79
Score	0%	56%

Review

The force exerted on an object due to gravity is called:

70% Answer Correctly

	mass
	potential energy
	weight
	density

Solution

Mass is an intrinsic property of matter and does not vary. Weight is the force exerted on the mass of an object due to gravity and a specific case of Newton's Second Law of Motion. Replace force with weight and acceleration with acceleration due to gravity on Earth (g) and the result is the formula for weight: W = mg or, substituting for g, weight equals mass multiplied by 9.8 m/s².

2 The radius of the axle is 3, the radius of the wheel is 8, and the blue box weighs 65 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	8.01 lbs.
	3 lbs.
	24.34 lbs.
	21.36 lbs.

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 8 and the output radius (where the resistance is being applied) is 3 for a mechanical advantage of \( \frac{8}{3} \) = 2.67

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{65 lbs.}{2.67} \) = 24.34 lbs.

3 If A = 9 ft., B = 1 ft., C = 4 ft., the green box weighs 35 lbs. and the blue box weighs 50 lbs., what does the orange box have to weigh for this lever to balance?

44% Answer Correctly

	33.13 lbs.
	265 lbs.
	66.25 lbs.
	35 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:

35 lbs. x 9 ft. = 50 lbs. x 1 ft. + f_C x 4 ft.

315 ft. lbs. = 50 ft. lbs. + f_C x 4 ft.

f_C = \( \frac{315 ft. lbs. - 50 ft. lbs.}{4 ft.} \) = \( \frac{265 ft. lbs.}{4 ft.} \) = 66.25 lbs.

Boyle's law defines the relationship between pressure and volume as:

57% Answer Correctly

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

Solution

Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional". Expressed as a formula, that's \(\frac{P_1}{P_2} = \frac{V_2}{V_1}\)

5 If this lever is in equilibrium with an effort force of 26.67 ft. lb. at the blue arrow and a resistance force of 8 ft. lb. at the green box, what is its mechanical advantage?

48% Answer Correctly

	0.15
	0.3
	0.9
	3.3

Solution

Mechanical advantage (MA) is the ratio by which effort force relates to resistance force. If both forces are known, calculating MA is simply a matter of dividing resistance force by effort force:

MA = \( \frac{F_r}{F_e} \) = \( \frac{8 ft.}{26.67 ft.} \) = 0.3

In this case, the mechanical advantage is less than one meaning that each unit of effort force results in just 0.3 units of resistance force. However, a third class lever like this isn't designed to multiply force like a first class lever. A third class lever is designed to multiply distance and speed at the resistance by sacrificing force at the resistance. Different lever styles have different purposes and multiply forces in different ways.