ASVAB Mechanical Comprehension Practice Test 325140 Results

Your Results Global Average
Questions 5 5
Correct 0 2.81
Score 0% 56%

Review

1

A screw is most like which of the following other simple machines?

50% Answer Correctly

first-class lever

inclined plane

block and tackle

wheel and axle
Solution

A screw is an inclined plane wrapped in ridges (threads) around a cylinder. The distance between these ridges defines the pitch of the screw and this distance is how far the screw advances when it is turned once. The mechanical advantage of a screw is its circumference divided by the pitch.

2 If the handles of a wheelbarrow are 1.0 ft. from the wheel axle and the load is concentrated at a point 1.5 ft. from the axle, how many pounds of load will a 260 lbs. force lift?
47% Answer Correctly
173.3
260
0
22
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. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{260 \times 1.0}{1.5} \)
\( F_r = \frac{260.0}{1.5} \)
\( F_r = 173.3 \)
3 How much resistance could a 190 lb. effort force lift using a block and tackle pulley that has 8 ropes supporting the resistance?
81% Answer Correctly
1522 lbs.
760 lbs.
3040 lbs.
1520 lbs.
Solution

The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 8. With a MA of 8, a 190 lbs. effort force could lift 190 lbs. x 8 = 1520 lbs. resistance.

4

Which of the following is the formula for hydraulic pressure?

58% Answer Correctly

P = FA2

P = F/A2

P = FA

P = F/A
Solution

Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).

5

Which of the following is not a modulus of elasticity?

47% Answer Correctly

shear modulus

stress modulus

stretch modulus

bulk modulus
Solution

The modulus of elasticity measures how much a material or structure will deflect under stress. Stretch modulus is longitudinal stretch (like stretching raw bread dough), shear modulus is longitudinal deflection (like the horizontal displacement of a stack of magzines when a heavy object is placed upon them), and bulk modulus is compression of volume (like the compression of a loaf of bread under a heavy can at the bottom of a grocery bag).