A sharpening bar weighing 300 g has a length l = 15 cm, a width b = 50 mm and a height h = 0.20 dm.

A sharpening bar weighing 300 g has a length l = 15 cm, a width b = 50 mm and a height h = 0.20 dm. Determine the density of the thing from which the bar is made.

m = 300 g = 0.3 kg.

l = 15 cm = 0.15 m.

b = 50 mm = 0.05 m.

h = 0.2 dm = 0.02 m.

ρ -?

The density of a substance ρ is called a scalar physical quantity equal to the ratio of the mass of a body m to its volume V: ρ = m / V.

The sharpening bar has the shape of a rectangular parallelepiped, so its volume is expressed by the formula: V = l * b * h, where l is its length, b is the width of the bar, h is the height of the bar.

The formula for the density ρ will take the form: ρ = m / l * b * h.

ρ = 0.3 kg / 0.15 m * 0.05 m * 0.02 m = 2000 kg / m3.

Answer: the whetstone has a density of ρ = 2000 kg / m3.