ASVAB Mechanical Comprehension Practice Test 948047 Results

Your Results Global Average
Questions 5 5
Correct 0 3.12
Score 0% 62%

Review

1 If the green box weighs 40 lbs. and is 3 ft. from the fulcrum, how far from the fulcrum would a 50 lbs. force need to be applied to balance the lever?
58% Answer Correctly
4.8 ft.
2.4 ft.
13 ft.
0.6 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:

Rada = Rbdb

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

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{40 lbs. \times 3 ft.}{50 lbs.} \) = \( \frac{120 ft⋅lb}{50 lbs.} \) = 2.4 ft.

2

On Earth, acceleration due to gravity (g) is approximately __________. 

81% Answer Correctly

1 m/s

9.8 m/s2

1 m/s2

6.67 x 10-11 m/s2
Solution

Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects:  \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s2. 

3 If A = 12 ft., B = 1 ft., C = 7 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
17.62 lbs.
52.86 lbs.
158.57 lbs.
2 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:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

35 lbs. x 12 ft. = 50 lbs. x 1 ft. + fC x 7 ft.

420 ft. lbs. = 50 ft. lbs. + fC x 7 ft.

fC = \( \frac{420 ft. lbs. - 50 ft. lbs.}{7 ft.} \) = \( \frac{370 ft. lbs.}{7 ft.} \) = 52.86 lbs.

4 If the radius of the axle is 7 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?
52% Answer Correctly
3
7
0.7
1.43
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 10 and the output radius (where the resistance is being applied) is 7 for a mechanical advantage of \( \frac{10}{7} \) = 1.43

5

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

66% Answer Correctly

exponential

logarithmic

inverse

linear
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.