ASVAB Mechanical Comprehension Practice Test 995518 Results

	Your Results	Global Average
Questions	5	5
Correct	0	3.21
Score	0%	64%

Review

1 If A = 8 ft. and the green box weighs 45 lbs. what is the torque acting on the A side of this lever?

74% Answer Correctly

	1080 ft⋅lb
	720 ft⋅lb
	360 ft⋅lb
	120 ft⋅lb

Solution

For a lever, torque is weight x distance from the fulcrum which, in this case, is: 45 ft. x 8 lbs. = 360 ft⋅lb

Tension is a force that does which of the following?

75% Answer Correctly

	heats up an object
	stretches an object
	compacts an object
	slows an object

Solution

Tension is a force that stretches or elongates something. When a cable or rope is used to pull an object, for example, it stretches internally as it accepts the weight that it's moving. Although tension is often treated as applying equally to all parts of a material, it's greater at the places where the material is under the most stress.

3 If the green box weighs 10 lbs. and 65 lbs. of force is applied 3 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

	0 ft.
	6.5 ft.
	19.5 ft.
	78 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 = \( \frac{R_bd_b}{R_a} \) = \( \frac{65 lbs. \times 3 ft.}{10 lbs.} \) = \( \frac{195 ft⋅lb}{10 lbs.} \) = 19.5 ft.

The mechanical advantage of a block and tackle is equal to which of the following?

69% Answer Correctly

	the number of connecting ropes
	the number of pulleys
	the number of input forces
	the number of loads

Solution

Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

Which class of lever offers no mechanical advantage?

45% Answer Correctly

	second
	none of these, all levers offer mechanical advantage
	third
	first

Solution

A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.