ASVAB Mechanical Comprehension Practice Test 259093 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.06
Score	0%	61%

Review

A box is resting on a smooth floor. Static friction is present:

59% Answer Correctly

	if the coefficient of friction is greater than one
	only if normal force is present
	at all times
	when an attempt is made to move the box

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).

Which of the following will increase the mechanical advantage of a second-class lever?

55% Answer Correctly

	move the object being lifted closer to the fulcrum
	move the object being lifted farther away from the fulcrum
	decrease the length of the lever
	move the fulcrum between the force and the object being lifted

Solution

A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.

3 If A = 9 ft. and the green box weighs 50 lbs. what is the torque acting on the A side of this lever?

75% Answer Correctly

	450 ft⋅lb
	1350 ft⋅lb
	0 ft⋅lb
	112 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 50 ft. x 9 lbs. = 450 ft⋅lb

A fixed pulley has a mechanical advantage of:

68% Answer Correctly

	2
	-1
	1
	0

Solution

A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.

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

48% Answer Correctly

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