What weight must be placed at point A to balance the lever if B weighs 150 pounds?

• A. 50 lbs
• B. 75 lbs
• C. 100 lbs
• D. 150 lbs

Answer: (B)

To find the weight that must be placed at point A to balance the lever, we can utilize the principle of moments, which states that for a lever to be in balance, the moments (or torque) around a pivot point must be equal.

Assuming point A and point B are spaced at equal distances from the pivot, we determine that the moment exerted by the weight at point B must equal the moment exerted by the weight at point A. The moment is calculated by multiplying the weight by the distance from the pivot point.

If point B weighs 150 lbs, and assuming it's at a distance of 1 unit from the pivot, the moment at point B would be 150 lbs * 1 unit = 150 lb-units. To find the weight at point A that will balance this, let’s assume it is placed at the same distance from the pivot. Therefore, we set the moment at point A equal to that of point B.

Using the equation:

Weight at A * Distance from pivot = Weight at B * Distance from pivot

Since both distances are equal, we can simplify to:

Weight at A = Weight at B

For the lever to be balanced, the equation simplifies to determining the correct multiple of