ASVAB Mechanical Comprehension Practice Test 543279 Results

Your Results Global Average
Questions 5 5
Correct 0 3.22
Score 0% 64%

Review

1

Which class of lever offers no mechanical advantage?

45% Answer Correctly

first

none of these, all levers offer mechanical advantage

second

third
Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.

2 What is the power output of a 9 hp engine that's 45% efficient?
40% Answer Correctly
6682.5 \( \frac{ft⋅lb}{s} \)
4455 \( \frac{ft⋅lb}{s} \)
2227.5 \( \frac{ft⋅lb}{s} \)
0 \( \frac{ft⋅lb}{s} \)
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 \( \frac{ft⋅lb}{s} \)
\( P_{o} = \frac{E \times P_{i}}{100} = \frac{45 \times 4950 \frac{ft⋅lb}{s}}{100} \) \( = \frac{222750 \frac{ft⋅lb}{s}}{100} \) = 2227.5 \( \frac{ft⋅lb}{s} \)
3

Which of the following is not a type of bridge?

74% Answer Correctly

truss

arch

cable

block
Solution

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

4 If input effort is 300 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 2?
79% Answer Correctly
1200ft⋅lb
600 ft⋅lb
150ft⋅lb
2400ft⋅lb
Solution
Mechanical advantage is the ratio of output force to input force and tells us by how many times a machine multiplies input effort. So, a machine with a mechanical advantage of 2 will multiply an input effort of 300 ft⋅lb by 2 to produce an output effort of 600 ft⋅lb.
5

Friction resists movement in a direction __________ to the movement.

81% Answer Correctly

parallel

normal

opposite

perpendicular
Solution

Friction resists movement. Kinetic (also called sliding or dynamic) friction resists movement in a direction opposite to the movement. Because it opposes movement, kinetic friction will eventually bring an object to a stop. An example is a rock that's sliding across ice.