ASVAB Mechanical Comprehension Practice Test 778752 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.19
Score	0%	64%

Review

The force required to initally get an object moving is __________ the force required to keep it moving.

76% Answer Correctly

	higher than
	lower than
	the same as
	opposite

Solution

For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).

2 If the green box weighs 10 lbs. and 35 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow, how far from the fulcrum would the green box need to be placed to balance the lever?

55% Answer Correctly

	8.75 ft.
	17.5 ft.
	52.5 ft.
	0 ft.

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 d_a, our missing value, and plugging in our variables yields:

d_a = \( \frac{R_bd_b}{R_a} \) = \( \frac{35 lbs. \times 5 ft.}{10 lbs.} \) = \( \frac{175 ft⋅lb}{10 lbs.} \) = 17.5 ft.

What type of load doesn't create specific stress points or vary with time?

60% Answer Correctly

	impact load
	static uniformly distributed 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.

What defines the mechanical advantage of a first class lever?

65% Answer Correctly

	output distance
	output force
	input force
	position of the fulcrum

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.

5 If 45 lbs. of force is applied 5 ft. from the fulcrum at the blue arrow and the green box is 4 ft. from the fulcrum, how much would the green box have to weigh to balance the lever?

62% Answer Correctly

	28.13 lbs.
	225 lbs.
	56.25 lbs.
	0 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_a, our missing value, and plugging in our variables yields:

R_a = \( \frac{R_bd_b}{d_a} \) = \( \frac{45 lbs. \times 5 ft.}{4 ft.} \) = \( \frac{225 ft⋅lb}{4 ft.} \) = 56.25 lbs.