ASVAB Mechanical Comprehension Practice Test 95080 Results

Your Results Global Average
Questions 5 5
Correct 0 2.92
Score 0% 58%

Review

1

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

everywhere in the system

all of these are correct

the portions of the system at an altitude above the input

the portions of the system at an altitude below the input
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.

2 What is the power output of a 4 hp engine that's 75% efficient?
40% Answer Correctly
825 \( \frac{ft⋅lb}{s} \)
1650 \( \frac{ft⋅lb}{s} \)
4950 \( \frac{ft⋅lb}{s} \)
3300 \( \frac{ft⋅lb}{s} \)
Solution
\( Efficiency = \frac{Power_{out}}{Power_{in}} \times 100 \)
Solving for power out: \( P_{o} = \frac{E \times P_{i}}{100} \)
Knowing that 1 hp = 550 \( \frac{ft⋅lb}{s} \), Pi becomes 4 hp x 550 \( \frac{ft⋅lb}{s} \) = 2200 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{75 \times 2200 \frac{ft⋅lb}{s}}{100} \) \( = \frac{165000 \frac{ft⋅lb}{s}}{100} \) = 1650 \( \frac{ft⋅lb}{s} \)
3

Force of friction due to kinetic friction is __________ the force of friction due to static friction.

40% Answer Correctly

higher than

lower than

opposite

the same as
Solution

The formula for force of friction (Ff) is the same whether kinetic or static friction applies: Ff = μFN. To distinguish between kinetic and static friction, μk and μs are often used in place of μ.

4 How much resistance could a 50 lb. effort force lift using a block and tackle pulley that has 8 ropes supporting the resistance?
82% Answer Correctly
394 lbs.
400 lbs.
200 lbs.
360 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 50 lbs. effort force could lift 50 lbs. x 8 = 400 lbs. resistance.

5

Hydraulics is the transmission of force through the use of which of the following?

73% Answer Correctly

liquids

gear systems

torque

air pressure
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).