Units (Solids, Liquids and Gases)
5 marks · NormalA rectangular wooden block has a mass of 0.96 kg. It has dimensions 0.20 m (length), 0.10 m (width), and 0.08 m (height). The block rests flat on the ground.
Calculate the density of the wooden block in kg/m³.
Calculate the pressure the block exerts on the ground, assuming the whole lower face touches the ground. Give your answer in pascals (Pa).
State the equation linking pressure, force and area.
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) 600 kg/m³ · must show Density = mass/volume, correct use of units
(b) 600 Pa · must show Pressure = force/area, use of weight as force
(c) p = F / A · must show Correct formula in symbols or words
Common mistakes: Incorrect unit conversions; Area calculation error
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly calculates volume of the block.
A1 (a) · 1 mark · Correct substitution and answer for density in correct units.
M2 (b) · 1 mark · Uses correct value for force (weight = m × g) and area for pressure calculation. (follow-through)
A2 (b) · 1 mark · Correct answer for pressure (within tolerance) with unit. (follow-through)
B1 (c) · 1 mark · States correct formula p = F/A (or equivalent in words/symbols).
Worked solution
a) Volume = length × width × height = 0.20 m × 0.10 m × 0.08 m = 0.0016 m³.
b) Force = weight = mass × g = 0.96 kg × 10 N/kg = 9.6 N. Area = 0.20 m × 0.10 m = 0.02 m².
c) The equation linking pressure, force and area is p = F / A.