Density and how to measure it
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The teaching part (1 min) is free to watch. A free account opens the whole lecture: 1 worked example, 7 practice questions, 1 real past-paper question with the answer explained, the mistakes that lose marks, the full-marks tip, a one-card summary and a quick quiz.
What this lecture covers
- Why does a ship float?
- Density
- Three forms of one equation
Read the transcript of the teaching part
Last time
Before we start: last time, in Mass, weight and density, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.
Why does a ship float?
A steel nail sinks, yet a steel ship floats. It is not about how heavy something is. It is about how much mass is packed into each bit of space. That idea is called density.
Density
Density is the mass of a substance in each unit of volume. The symbol for density is the Greek letter rho, and the equation is rho equals m over V. The units are grams per cubic centimetre, or kilograms per cubic metre. A dense material has lots of mass in a small volume, like lead. A low density material is light for its size, like polystyrene.
Three forms of one equation
Density is mass divided by volume. Mass is density times volume. Volume is mass divided by density.
How often it comes up
How often Cambridge has asked each part, counted by ExamYard from every past paper in its question bank: Calculating density.
Chapter 1.3: Mass, weight and density
- Mass, weight and gravitational field strength 5 min
- Density and how to measure it 5 min
Also for O Level Physics 5054
Which topics come up most in O Level Physics 5054 past papers, counted from every paper since 2004.