A ball of mass 4kg is lightly dropped into a tub with a base of 1m^2. After it sinks to the bottom, the water rises by 2.5mm. Determine the density of the ball. a) 40 kg/L
b) 4.4 kg/L
c) 1.6 kg/L​

Let h be the height of the water in the tube. Then the total volume of water is

(h m) (1 m²) = h m³

After dropping the ball into the water, the height of the water changes to

h m + 2.25 mm = (h + 0.0025) m

and so the contents of the tub take up (h + 0.0025) m³ of volume.

This means the ball displaces

(h + 0.0025) m³ - h m³ = 0.0025 m³

of water, which is to say that this is volume of the ball.

With a mass of 4 kg, you would find its density to be

(4 kg) / (0.0025 m³) = (4 kg) / (2.5 L) = 1.6 kg/L

force tends to be low and long diustance masses are high