The cast iron ball has a mass of 4.2 kg with a volume of 700 cm 3. Determine if this ball has a cavity inside.

In order to find the density ρ (in kg / m³) of a homogeneous body, the formula ρ = m / V is used, where m is the mass of the body (in kg), V is its volume (in m³). As you know, the density of cast iron, depending on the brand, can be equal from 6800 kg / m³ to 7800 kg / m³. The task is given: m = 4.2 kg and V = 700 cm³. Determine the density of the cast iron ball. Using the equality 1 m³ = 1,000,000 cm³, we express the volume in m³: V = 700 cm³ = (700: 1,000,000) m³ = 0.0007 m³. Let’s calculate: ρ = m / V = (4.2 kg) / (0.0007 m³) = 6000 kg / m³. Since 6000 <6800, there is a cavity in the ball.