Solids, Liquids and Gases
5 marks · NormalA student places a wooden block on a bench and wants to find the pressure it exerts on the surface. After, she measures the density of a sample of oil.
The wooden block has a mass of 2.5 kg and its base measures 0.10 m by 0.20 m. Calculate the pressure the block exerts on the bench. Give your answer in pascals (Pa).
She uses a measuring cylinder to find the volume of a sample of oil. The oil mass is 50 g and its volume is 56 mL. Calculate the density of the oil in 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) 125 Pa · must show method for area, method for pressure, correct unit Pa
(b) 893 kg/m³ · must show mass converted to kg, volume converted to m³, density formula
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly uses area = length × width.
M2 (a) · 1 mark · Substitutes values correctly into pressure = force/area formula.
A1 (a) · 1 mark · Correct answer with correct units (Pa), allow 123–127 Pa.
M3 (b) · 1 mark · Converts mass to kg and volume to m³; substitutes into density formula.
A2 (b) · 1 mark · Correct answer with suitable rounding and unit (accept 880–900 kg/m³).
Worked solution
a) Area of block = 0.10 m × 0.20 m = 0.020 m².
Note error: should be 25 N / 0.20 m² = 125 Pa (correction).
b) Mass = 50 g = 0.050 kg; Volume = 56 mL = 0.000056 m³.
Rounded answer: 893 kg/m³.