ASVAB Mechanical Comprehension Practice Test 312643 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.85
Score	0%	57%

Review

Which of the following statements about drag is false?

58% Answer Correctly

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

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.

Depending on where you apply effort and resistance, the wheel and axle can multiply:

45% Answer Correctly

	power or distance
	force or speed
	force or distance
	speed or power

Solution

If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.

3 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle and the load is concentrated at a point 1.5 ft. from the axle, how many pounds of load will a 220 lbs. force lift?

47% Answer Correctly

	0
	-48.7
	366.7
	132

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: F_ed_e = F_rd_r. In this problem we're looking for resistance force:
\( F_r = \frac{F_e d_e}{d_r} \)
\( F_r = \frac{220 \times 2.5}{1.5} \)
\( F_r = \frac{550.0}{1.5} \)
\( F_r = 366.7 \)

The force required to initally get an object moving is __________ the force required to keep it moving.

76% Answer Correctly

	opposite
	the same as
	higher than
	lower than

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).

The measure of how much of the power put into a machine is turned into movement or force is called:

56% Answer Correctly

	power
	mechanical advantage
	force multiplication
	efficiency

Solution

The efficiency of a machine describes how much of the power put into the machine is turned into movement or force. A 100% efficient machine would turn all of the input power into output movement or force. However, no machine is 100% efficient due to friction, heat, wear and other imperfections that consume input power without delivering any output.