ASVAB Mechanical Comprehension Practice Test 809361 Results

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

Review

1 If the green box weighs 65 lbs. and is 5 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 6 ft.?
62% Answer Correctly
54.17 lbs.
10 lbs.
390 lbs.
13.54 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 Rb, our missing value, and plugging in our variables yields:

Rb = \( \frac{R_ad_a}{d_b} \) = \( \frac{65 lbs. \times 5 ft.}{6 ft.} \) = \( \frac{325 ft⋅lb}{6 ft.} \) = 54.17 lbs.

2 How much work can a 2 hp engine do in 7 seconds?
53% Answer Correctly
3 ft⋅lb
7700 ft⋅lb
0 ft⋅lb
1 ft⋅lb
Solution
Horsepower (hp) is a common measure of power output for complex machines. By definition, a 1 hp machine does 550 ft⋅lb of work in 1 second: 1 hp = 550 ft⋅lb/s. Substituting the variables for this problem gives us:
\( W = 2 hp \times 550 \frac{ft⋅lb}{s} \times 7s = 7700 ft⋅lb \)
3

For a hydraulic system, pressure applied to the input of the system will increase the pressure in which parts of the system?

59% Answer Correctly

the portions of the system at an altitude below the input

all of these are correct

the portions of the system at an altitude above the input

everywhere in the system
Solution

Pascal's law states that a pressure change occurring anywhere in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere. For a hydraulic system, this means that a pressure applied to the input of the system will increase the pressure everywhere in the system.

4

Which of the following is not a type of bridge?

74% Answer Correctly

block

cable

truss

arch
Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

5

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

the number of loads

the number of pulleys

the number of connecting ropes

the number of input forces
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.