A copper ball with a volume of 120 cm3 weighs 8.5 N. Is it a solid ball or does it have a void inside?

Let’s assume that the ball is solid, with no voids inside. If the density of copper is ρ = 8900 kg / m³, then the mass of the ball m, kg, will be equal to

m = ρ * V = 8900 * (120 * 10 ^ (- 6)) = 1.068 kg.

The weight of the ball P, H, is determined by the formula

P = m * g,

where g = 9.81 m / s² is the acceleration of gravity at the Earth’s surface.

P = 1.068 * 9.81 = 10.5 N.

But according to the condition, the ball weighs only 8.5 N, so it cannot be solid, which means it has emptiness inside.