ASVAB Mechanical Comprehension Practice Test 832985 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.09
Score	0%	62%

Review

Which of the following is not a type of structural load?

49% Answer Correctly

	live load
	occupancy load
	dead load
	wind load

Solution

Dead load is the weight of the building and materials, live load is additional weight due to occupancy or use, snow load is the weight of accumulated snow on a structure and wind load is the force of wind pressures against structure surfaces.

2 What is the efficiency of a machine has work input of 110 ft⋅lb and work output of 44 ft⋅lb?

67% Answer Correctly

	0%
	80%
	20%
	40%

Solution

Due to friction, a machine will never be able to utilize 100% of its work input. A certain percentage of that input will be lost in overcoming friction within the machine. Effeciency is a measure of how much of a machine's work input can be turned into useful work output and is calculated by dividing work output by work input and multiplying the result by 100:
\( Efficiency = \frac{Work_{out}}{Work_{in}} \times 100 \) \( = \frac{44 ft⋅lb}{110 ft⋅lb} \times 100 \) \( = 40% \) %

The force amplification achieved by using a tool, mechanical device or machine system is called:

80% Answer Correctly

	mechanical advantage
	work
	power
	efficiency

Solution

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Such a device utilizes input force and trades off forces against movement to amplify and/or change its direction.

If the handles of a wheelbarrow are 3 ft. from the wheel axle, what force must you exert to lift the handles if it's carrying a 270 lb. load concentrated at a point 0.5 ft. from the axle?

56% Answer Correctly

	0.83 lbs
	45 lbs
	90 lbs
	810 lbs

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. Plugging in the variables from this problem yields:

F_e x 3 ft. = 270 lbs x 0.5 ft
F_e = 135 ft-lb. / 3 ft
F_e= 45 lbs

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

56% Answer Correctly

	mechanical advantage
	power
	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.