The mass of the copper ball is 12 kg, and its volume is 4 dm³. Is this ball solid or hollow? What is the average density of the ball?

Given:
m = 12 kilograms is the mass of the copper ball;
V = 4 dm3 = 0.004 m3 (cubic meters) – the volume that the copper ball occupies;
ro = 8900 kg / m3 – copper density.
It is required to determine whether the ball has cavities, and ro (av) is the average density of the ball.
Let us find the volume that would be occupied by a copper ball of mass m:
V1 = m / ro = 12/8900 = 0.0013 m3 (the result has been rounded to one ten thousandth).
Since V1 <V (0.0013 <0.004), it means that there are cavities in the ball.
Determine the average density of the ball:
ro (sr) = m / V = ​​12 / 0.004 = 3000 kg / m3 (kilogram per cubic meter).
Answer: there are cavities in the ball, the average density of the ball is 3000 kg / m3.