FIA Aircraft Performance Practice Test

To determine the weight needed at point B to balance the lever with a weight of 40 lbs at point A, it is essential to use the principle of moments. The principle states that for a lever to be in equilibrium, the clockwise moments about a pivot must equal the counterclockwise moments.

Assuming that point A and point B are at equal distances from the pivot (fulcrum), the relationship can be established using the formula:

Moment = Weight × Distance

If Weight A is 40 lbs and is located at point A, the equal balancing force needed at point B would also need to maintain the necessary moment balance. To balance the lever, the moments caused by the weights must be equal. Therefore, the equation would look like:

Weight A (40 lbs) × Distance from pivot = Weight B × Distance from pivot.

If we consider the distances equal, we set the weights equal to each other. This means that to balance 40 lbs at point A, point B would need a greater weight due to being placed at a greater distance from the pivot.

In this scenario, if point B requires a weight of 80 lbs to create an equivalent moment in the opposite direction, it stands to reason that the correct choice is indeed