ASVAB Mechanical Comprehension Practice Test 700315 Results

	Your Results	Global Average
Questions	5	5
Correct	0	2.84
Score	0%	57%

Review

1 If the handles of a wheelbarrow are 0.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 230 lbs. load concentrated at a point 1.5 ft. from the axle?

52% Answer Correctly

	76.7
	33
	115
	690

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 effort force:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{230 \times 1.5}{0.5} \)
\( F_e = \frac{345.0}{0.5} \)
\( F_e = 690 \)

What is work?

60% Answer Correctly

	Force per unit time
	Force per unit distance
	The movement of an object by a force
	The potential for exertion

Solution

Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done. By definition, work is the displacement of an object resulting from applied force.

3 How much work can a 7 hp engine do in 3 seconds?

52% Answer Correctly

	11550 ft⋅lb
	2 ft⋅lb
	0 ft⋅lb
	28 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:
\( W = 7 hp \times 550 \frac{ft⋅lb}{s} \times 3s = 11550 ft⋅lb \)

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

51% Answer Correctly

	increases force
	decreases distance
	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.

Which of these is the formula for kinetic energy?

68% Answer Correctly

	\(KE = mgh\)
	\(KE = {1 \over 2}mv^2\)
	\(KE = {m \over v^2 }\)
	\(KE = {1 \over 2}mh^2\)

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.