ASVAB Mechanical Comprehension Practice Test 81982 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.70
Score	0%	54%

Review

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	none of these, all levers offer mechanical advantage
	second
	first
	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.

The science that deals with motion and the forces that produce motion is called which of the following?

57% Answer Correctly

	physics
	mechanics
	engineering
	aeronautics

Solution

Mechanics deals with motion and the forces that produce motion.

Which of the following is not true of a first-class lever?

51% Answer Correctly

	decreases distance
	increases force
	changes the direction of force
	increases distance

Solution

A first-class lever is used to increase force or distance while changing the direction of the force. The lever pivots on a fulcrum and, when a force is applied to the lever at one side of the fulcrum, the other end moves in the opposite direction. The position of the fulcrum also defines the mechanical advantage of the lever. If the fulcrum is closer to the force being applied, the load can be moved a greater distance at the expense of requiring a greater input force. If the fulcrum is closer to the load, less force is required but the force must be applied over a longer distance. An example of a first-class lever is a seesaw / teeter-totter.

Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?

64% Answer Correctly

	do the work in 2 minutes
	do the work in 3 minutes
	do 100 ft. lb. of work in 4 minutes 12 seconds
	do 25 ft. lb. of work in 2 minutes 5 seconds

Solution

Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.

5 How much work can a 9 hp engine do in 8 seconds?

52% Answer Correctly

	0 ft⋅lb
	39600 ft⋅lb
	4 ft⋅lb
	18 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:
\( W = 9 hp \times 550 \frac{ft⋅lb}{s} \times 8s = 39600 ft⋅lb \)