ASVAB Mechanical Comprehension Practice Test 542810 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.87
Score	0%	57%

Review

1 How much work can a 4 hp engine do in 4 seconds?

52% Answer Correctly

	8 ft⋅lb
	1 ft⋅lb
	2 ft⋅lb
	8800 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:
\( W = 4 hp \times 550 \frac{ft⋅lb}{s} \times 4s = 8800 ft⋅lb \)

2 A 370 lb. barrel is rolled up a 14 ft. ramp to a platform that's 1 ft. tall. What effort is required to move the barrel?

53% Answer Correctly

	26.4 lbs.
	13.2 lbs.
	52.9 lbs.
	29.4 lbs.

Solution

This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:

F_ed_e = F_rd_r

Plugging in the variables from this problem yields:

F_e x 14 ft. = 370 lbs. x 1 ft.
F_e = \( \frac{370 ft⋅lb}{14 ft.} \) = 26.4 lbs.

Which of the following statements about drag is false?

58% Answer Correctly

	the amount of drag depends on the speed of an object
	slower objects experience more drag than faster objects
	the amount of drag depends on the shape of an object
	drag occurs during movement through a fluid

Solution

Drag is friction that opposes movement through a fluid like liquid or air. The amount of drag depends on the shape and speed of the object with slower objects experiencing less drag than faster objects and more aerodynamic objects experiencing less drag than those with a large leading surface area.

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

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.

A box is resting on a smooth floor. Static friction is present:

59% Answer Correctly

	if the coefficient of friction is greater than one
	only if normal force is present
	at all times
	when an attempt is made to move the box

Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).