Units (Solids, Liquids and Gases)
4 marks · EasyA solid metal block is dropped into a tank of water so that it sinks to the bottom. The block has a mass of 0.60 kg and a volume of 0.0002 m³.
Calculate the density of the metal block in kg/m³.
Use the equation for pressure in liquids to write down the formula linking pressure difference, height, density, and gravitational field strength.
Explain why the metal block sinks in water, using your answers.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 3000 kg/m³
(b) p = h × ρ × g
(c) The block sinks because its density is greater than that of water.
Common mistakes: incorrect units for density; mixing up mass and volume
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Writes correct formula and substitutes values: density = mass / volume = 0.60 / 0.0002.
A1 (a) · 1 mark · Gives the correct answer with correct unit: 3000 kg/m³. (follow-through)
B1 (b) · 1 mark · States the formula for pressure difference: p = h × ρ × g.
B2 (c) · 1 mark · Correctly explains that the block sinks because its density is greater than water's density.
Worked solution
a) Density = mass / volume = 0.60 kg / 0.0002 m³ = 3000 kg/m³.
b) The formula linking pressure difference, height, density and g is:
c) The density of water is about 1000 kg/m³. Since the block’s density (3000 kg/m³) is greater, it sinks.