ASVAB Mechanical Comprehension Practice Test 347148 Results

Your Results Global Average
Questions 5 5
Correct 0 3.36
Score 0% 67%

Review

1 If the green box weighs 45 lbs. and is 5 ft. from the fulcrum, how far from the fulcrum would a 25 lbs. weight need to be placed to balance the lever?
61% Answer Correctly
18 ft.
9 ft.
225 ft.
36 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:

Rada = Rbdb

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

db = \( \frac{R_ad_a}{R_b} \) = \( \frac{45 lbs. \times 5 ft.}{25 lbs.} \) = \( \frac{225 ft⋅lb}{25 lbs.} \) = 9 ft.

2

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

mechanics

aeronautics

engineering

physics
Solution

Mechanics deals with motion and the forces that produce motion.

3 If input effort is 300 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 6?
79% Answer Correctly
3600ft⋅lb
50ft⋅lb
1800 ft⋅lb
0ft⋅lb
Solution
Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 6 will multiply an input effort of 300 ft⋅lb by 6 to produce an output effort of 1800 ft⋅lb.
4 If a 25 lbs. weight is placed 1 ft. from the fulcrum at the blue arrow and the green box is 4 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
61% Answer Correctly
25 lbs.
2.08 lbs.
12.5 lbs.
6.25 lbs.
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:

Rada = Rbdb

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

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{25 lbs. \times 1 ft.}{4 ft.} \) = \( \frac{25 ft⋅lb}{4 ft.} \) = 6.25 lbs.

5 What is the mechanical advantage of this inclined plane if the length of the ramp is 21 ft. and the height of the green box is 3 ft.?
82% Answer Correctly
3
7
14
21
Solution

The mechanical advantage (MA) of an inclined plane is the effort distance divided by the resistance distance. In this case, the effort distance is the length of the ramp and the resistance distance is the height of the green box:

MA = \( \frac{d_e}{d_r} \) = \( \frac{21 ft.}{3 ft.} \) = 7