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Edexcel A Level Physics:復習筆記4.1 Density

Category: A-level課程, 教材筆記, 福利干貨 Date: 2022年10月9日下午3:13

Density is the?mass per unit volume?of an object
- Objects made from low-density materials typically have a lower mass
- For example, a balloon is less dense than a small bar of lead despite occupying a larger volume
The units of density depend on the units used for mass and volume:
- If the mass is measured in?g?and volume in?cm3, then the density will be in?g / cm3
- If the mass is measured in?kg?and volume in?m3, then the density will be in?kg / m3

4.2.1-Density-equation

4.2.1-Density-comparison

Gases are less dense than a solid

The volume of an object may not always be given directly, but can be calculated with the appropriate equation depending on the object’s shape

4.2.1-Volume-of-shapes

Volumes of common 3D shapes

A paving slab has a mass of 73 kg and dimensions 40 mm × 500 mm × 850 mm.

Calculate the density, in kg m-3?of the material from which the paving slab is made. WE-Density-question-image

WE-Density-answer-image

When converting a?larger?unit to a?smaller?one, you?multiply (×)
- E.g. 125 m = 125 × 100 = 12 500 cm
When you convert a?smaller?unit to a?larger?one, you?divide (÷)
- E.g. 5 g = 5 / 1000 = 0.005 or 5 × 10-3?kg
When dealing with squared or cubic conversions, cube or square the conversion factor too
- E.g. 1 mm3?= 1 / (1000)3?= 1 × 10-9?m3
- E.g. 1 cm3?= 1 / (100)3?= 1 × 10-6?m3