ASVAB Mechanical Comprehension Practice Test 853567 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.26
Score	0%	65%

Review

1 If you have a gear train with two gears, the first with 32 teeth and the second with 16 teeth, how many revolutions does the second gear make for each revolution of the first gear?

77% Answer Correctly

	0.7
	6
	5
	2

Solution

The gear ratio (V_r) of a gear train is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:

V_r = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)

In this problem, we have only two gears so the equation becomes:

V_r = \( \frac{N_1}{N_2} \) = \( \frac{32}{16} \) = 2

Which of the following statements about this pulley configuration is false?

48% Answer Correctly

	This is a block and tackle pulley configuration
	Only multiplies the effort force
	Mechanical advantage is the number of ropes that support the resistance
	Changes the direction of and multiplies the effort force

Solution

A block and tackle is a combination of one or more fixed pulleys and one or more movable pulleys where the fixed pulleys change the direction of the effort force and the movable pulleys multiply it. The mechanical advantage is equal to the number of times the effort force changes direction and can be increased by adding more pulley wheels to the system. An easy way to find the mechanical advantage of a block and tackle pulley system is to count the number of ropes that support the resistance.

3 If the handles of a wheelbarrow are 1.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 160 lbs. load concentrated at a point 0.5 ft. from the axle?

52% Answer Correctly

	80
	240
	27.7
	53.3

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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{160 \times 0.5}{1.5} \)
\( F_e = \frac{80.0}{1.5} \)
\( F_e = 53.3 \)

What type of load creates different stresses at different locations on a structure?

60% Answer Correctly

	non-uniformly distributed load
	static uniformly distributed load
	dynamic 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.

On Earth, acceleration due to gravity (g) is approximately __________.

81% Answer Correctly

	1 m/s²
	9.8 m/s²
	6.67 x 10^-11 m/s²
	1 m/s

Solution

Newton's Law of Univeral Gravitation defines the general formula for the attraction of gravity between two objects: \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) . In the specific case of an object falling toward Earth, the acceleration due to gravity (g) is approximately 9.8 m/s².