ASVAB Mechanical Comprehension Practice Test 674610 Results

Your Results Global Average
Questions 5 5
Correct 0 2.56
Score 0% 51%

Review

1

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

40% Answer Correctly

lower than

higher 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.

2 What is the power output of a 9 hp engine that's 80% efficient?
40% Answer Correctly
1320 \( \frac{ft⋅lb}{s} \)
8 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
3960 \( \frac{ft⋅lb}{s} \)
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 9 hp x 550 \( \frac{ft⋅lb}{s} \) = 4950 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{80 \times 4950 \frac{ft⋅lb}{s}}{100} \) \( = \frac{396000 \frac{ft⋅lb}{s}}{100} \) = 3960 \( \frac{ft⋅lb}{s} \)
3 If the handles of a wheelbarrow are 1.5 ft. from the wheel axle and the load is concentrated at a point 0.5 ft. from the axle, how many pounds of load will a 240 lbs. force lift?
47% Answer Correctly
720
-3.4
120
142.9
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:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{240 \times 1.5}{0.5} \)
\( F_r = \frac{360.0}{0.5} \)
\( F_r = 720 \)
4

A wedge converts force applied to its blunt end into force __________ its inclined surface.

57% Answer Correctly

opposite to

perpendicular to

along

parallel to
Solution

The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.

5 If the green arrow in this diagram represents 760 ft⋅lb of work, how far will the box move if it weighs 190 pounds?
72% Answer Correctly
95 ft.
4 ft.
380 ft.
8 ft.
Solution
The Law of Work states that the work put into a machine is equal to the work received from the machine under ideal conditions. In equation form, that's:

Win = Wout
Feffort x deffort = Fresistance x dresistance

In this problem, the effort work is 760 ft⋅lb and the resistance force is 190 lbs. and we need to calculate the resistance distance:

Win = Fresistance x dresistance
760 ft⋅lb = 190 lbs. x dresistance
dresistance = \( \frac{760ft⋅lb}{190 lbs.} \) = 4 ft.