ASVAB Mechanical Comprehension Practice Test 935996 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.38
Score	0%	68%

Review

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

80% Answer Correctly

	mechanical advantage
	power
	work
	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.

Collinear forces:

73% Answer Correctly

	are unrelated to each other
	pass through a common point
	act along the same line of action
	act in a common plane

Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

3 If the handles of a wheelbarrow are 2.5 ft. from the wheel axle, how many pounds of force must you exert to lift the handles if it's carrying a 270 lbs. load concentrated at a point 1.5 ft. from the axle?

52% Answer Correctly

	675
	162
	0
	91.9

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:
\( F_e = \frac{F_r d_r}{d_e} \)
\( F_e = \frac{270 \times 1.5}{2.5} \)
\( F_e = \frac{405.0}{2.5} \)
\( F_e = 162 \)

What type of load is sudden and for a relatively short duration?

70% Answer Correctly

	dynamic load
	impact load
	non-uniformly distributed load
	concentrated 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.

5 If the green box weighs 70 lbs. and is 4 ft. from the fulcrum, how much force would need to be applied at the blue arrow to balance the lever if the arrow's distance from the fulcrum is 6 ft.?

62% Answer Correctly

	11.67 lbs.
	46.67 lbs.
	186.67 lbs.
	93.33 lbs.

Solution

To balance this lever the torques at the green box and the blue arrow 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 green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.

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

R_b = \( \frac{R_ad_a}{d_b} \) = \( \frac{70 lbs. \times 4 ft.}{6 ft.} \) = \( \frac{280 ft⋅lb}{6 ft.} \) = 46.67 lbs.