ASVAB Mechanical Comprehension Practice Test 434355 Results

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

Review

1 If the radius of the axle is 5 and the radius of the wheel is 10, what is the mechanical advantage of this wheel and axle configuration?

41% Answer Correctly

	10
	0.5
	-5
	5

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 5 and the output radius (where the resistance is being applied) is 10 for a mechanical advantage of \( \frac{5}{10} \) = 0.5

2 The radius of the axle is 5, the radius of the wheel is 6, and the blue box weighs 45 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	6.2 lbs.
	37.5 lbs.
	30 lbs.
	6 lbs.

Solution

The mechanical advantage of a wheel and axle is the input radius divided by the output radius:

MA = \( \frac{r_i}{r_o} \)

In this case, the input radius (where the effort force is being applied) is 6 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{6}{5} \) = 1.2

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{45 lbs.}{1.2} \) = 37.5 lbs.

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

76% Answer Correctly

	lower than
	higher than
	opposite
	the same as

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
	efficiency
	force multiplication
	mechanical advantage

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.

The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?

60% Answer Correctly

	mechanical advantage
	work-energy theorem
	conservation of mechanical energy
	Pascal's law

Solution

The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.