Density and Pressure
4 marks · Normal| Liquid | Mass (g) | Volume (cm^3) |
|---|---|---|
| A | 55 | 50 |
| B | 44 | 50 |
| C | 120 | 100 |
For each liquid, calculate its density in g/cm³. Write your answers in the table below.
| Liquid | Density (g/cm³) |
|---|---|
| A | |
| B | |
| C |
Liquid B is poured into a tank to form a layer 0.15 m deep. Calculate the pressure at the base of the tank caused by this layer. (Take gravitational field strength as 10 N/kg. Give answer in pascals. 1 g/cm³ = 1000 kg/m³.)
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) A: 1.10; B: 0.88; C: 1.20 · must show All densities correct to 2 dp
(b) 1320 Pa · must show Correct density conversion, Substitution into p = hρg
Common mistakes: Incorrect unit conversion for density; Using wrong depth or density in pressure calculation
Show mark scheme and worked solution
Marking points
M1a (a) · 1 mark · Density for at least two liquids correct (mass/volume), values correct to 2 dp
A1a (a) · 1 mark · All three densities correct and neatly filled in table
M1b (b) · 1 mark · Converts g/cm³ to kg/m³ and substitutes into p = hρg
A1b (b) · 1 mark · Calculates pressure correctly to 2 significant figures, includes unit
Worked solution
a) A: 55/50 = 1.10 g/cm³ B: 44/50 = 0.88 g/cm³ C: 120/100 = 1.20 g/cm³
b) For B: density = 0.88 × 1000 = 880 kg/m³ p = h × ρ × g = 0.15 × 880 × 10 = 1320 Pa