ASVAB Mechanical Comprehension Practice Test 331141 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.98
Score	0%	60%

Review

1 The radius of the axle is 5, the radius of the wheel is 10, and the blue box weighs 25 lbs. What is the effort force necessary to balance the load?

53% Answer Correctly

	15 lbs.
	12.5 lbs.
	5 lbs.
	10 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 10 and the output radius (where the resistance is being applied) is 5 for a mechanical advantage of \( \frac{10}{5} \) = 2.0

MA = \( \frac{load}{effort} \) so effort = \( \frac{load}{MA} \) = \( \frac{25 lbs.}{2.0} \) = 12.5 lbs.

Which of these will have the most impact on the kinetic energy of an object?

54% Answer Correctly

	its mass
	its speed
	its weight
	its direction

Solution

Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

	the number of connecting ropes
	the number of input forces
	the number of pulleys
	the number of loads

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?

45% Answer Correctly

	kinetic energy
	acceleration
	total mechanical energy
	potential energy

Solution

As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.

5 If input effort is 800 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 3?

79% Answer Correctly

	600ft⋅lb
	4800ft⋅lb
	2400 ft⋅lb
	1200ft⋅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 3 will multiply an input effort of 800 ft⋅lb by 3 to produce an output effort of 2400 ft⋅lb.