A box of negligible mass rests at the left end of a 2.00-m, 25.0-kg plank (Fig. 11.21).

Question:

A box of negligible mass rests at the left end of a 2.00-m, 25.0-kg plank (Fig. 11.21). The width of the box is 75.0 cm, and sand is to be distributed uniformly throughout it. The center of gravity of the non-uniform plank is 50.0 cm from the right end. What mass of sand should be put into the box so that the plank balances horizontally on a fulcrum placed just below its midpoint?