OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Sensing
Mechanical Properties of Materials
Waves and Quantum Behaviour
Space, Time and Motion
Creating Models
Out Into Space
Our Place in the Universe
Matter: Very Simple
Matter: Hot or Cold
Electromagnetism
Charge and Field
Probing Deep Into Matter
Ionising Radiation and Risk
Analysis
Significant figures and mathematical processing
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on significant figures in measurements and calculated results, decimal places for a mean, standard form and calculator entry, percentage change, scaling R = ρL/A, rearranging E = mc² and T = 2π√(L/g), order of magnitude calculations, and the symbols ∝, Δ, ≈, ≪ and ≫.
What you need to know
Answer each one before you reveal it.
What is meant by the symbol ∝ between two quantities, and by Δ written before a quantity?
To how many significant figures should a calculated result be quoted?
Questions from this subtopic
Each one with the model answer underneath.
- 1
To how many significant figures should a calculated result be quoted?
Model answer
To the same number of significant figures as the least precise measurement it was calculated from.
- 2
How many significant figures does the value 0.003 40 m contain?
Model answer
It contains three significant figures, because leading zeros only fix the decimal place while the trailing zero is a measured digit.
- 3
What is the difference between recording a length as 2.5 cm and as 2.50 cm?
Model answer
The first claims the length is known to the nearest 0.1 cm and the second to the nearest 0.01 cm, so they state different resolutions.
- 4
Express 0.045 678 9 m to three significant figures.
Model answer
It is 0.0457 m.
- 5
A block of mass 24.0 g has a volume of 3.2 cm³. Calculate its density and quote it to an appropriate number of significant figures.
Model answer
The density is 24.0 ÷ 3.2 = 7.5 g cm⁻³, quoted to two significant figures because the volume is known to only two.
- 6
To how many decimal places should the mean of a set of repeated readings be quoted?
Model answer
To the same number of decimal places as the individual readings, since averaging cannot improve the resolution of the instrument.
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