Two balls, lead and iron, of equal mass are suspended from the balance beam.

Two balls, lead and iron, of equal mass are suspended from the balance beam. Will the balance of the balance be upset if the balls are immersed in water?

After the balls are lowered into the water, their weight will change, since they will be acted upon by the buoyancy force (Archimedean force) from the side of the water. This force is equal to F = ro * g * V, where ro is the density of water, g is the gravitational constant, V is the volume of the ball. That is, the larger the volume of the ball, the greater the buoyancy force will act on it, the less it will weigh. Since the balls are of the same mass, the density of lead is about 11,000 kg / m ^ 3, and iron is about 8,000 kg / m ^ 3, the volume of the lead ball is less than the iron ball, which means that a large Archimedean force will act on the iron ball, which will reduce its weight.
The correct answer is to drag the lead ball.