ASVAB Mechanical Comprehension Practice Test 415936 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.49
Score	0%	70%

Review

Which of the following is the formula for gravitational potential energy?

61% Answer Correctly

	\(PE = mgh\)
	\(PE = { 1 \over 2} mg^2\)
	\(PE = mg^2h\)
	\(PE = { 1 \over 2} mv^2\)

Solution

Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s²).

What type of load acts on a relatively small area of a structure?

74% Answer Correctly

	dynamic load
	concentrated load
	non-uniformly distributed load
	impact load

Solution

A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.

Which of the following is not a type of bridge?

74% Answer Correctly

	block
	arch
	cable
	truss

Solution

The six basic bridge forms are beam, truss, arch, cantilever, cable, and suspension.

4 If a 35 lbs. weight is placed 7 ft. from the fulcrum at the blue arrow and the green box is 8 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

61% Answer Correctly

	15.31 lbs.
	30.63 lbs.
	7.66 lbs.
	245 lbs.

Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

R_ad_a = R_bd_b

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for R_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{35 lbs. \times 7 ft.}{8 ft.} \) = \( \frac{245 ft⋅lb}{8 ft.} \) = 30.63 lbs.

5 If input effort is 100 ft⋅lb, what output effort will be produced by a machine with a mechanical advantage of 2?

79% Answer Correctly

	50ft⋅lb
	200 ft⋅lb
	0ft⋅lb
	800ft⋅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 2 will multiply an input effort of 100 ft⋅lb by 2 to produce an output effort of 200 ft⋅lb.