ASVAB Mechanical Comprehension Practice Test 675301 Results

Your Results Global Average
Questions 5 5
Correct 0 3.16
Score 0% 63%

Review

1 What is the mechanical advantage of this inclined plane if the length of the ramp is 56 ft. and the height of the green box is 8 ft.?
82% Answer Correctly
8.5
10.5
7.7
7

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 = \( \frac{d_e}{d_r} \) = \( \frac{56 ft.}{8 ft.} \) = 7


2

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

810 lbs

90 lbs

45 lbs

0.83 lbs


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: Fede = Frdr. Plugging in the variables from this problem yields:

Fe x 3 ft. = 270 lbs x 0.5 ft
Fe = 135 ft-lb. / 3 ft 
Fe = 45 lbs


3

Two or more pulleys used together are called:

71% Answer Correctly

block and tackle

gears

wheel and axle

third-class lever


Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement.  So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.


4 If 35 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 1 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?
62% Answer Correctly
43.75 lbs.
58.33 lbs.
350 lbs.
175 lbs.

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

Ra = \( \frac{R_bd_b}{d_a} \) = \( \frac{35 lbs. \times 5 ft.}{1 ft.} \) = \( \frac{175 ft⋅lb}{1 ft.} \) = 175 lbs.


5

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

speed or power

force or speed

force or distance

power or distance


Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.