BRAINCAKEEstimating Physical Quantities
Physicists often need a quick estimate of a quantity: an approximate value found using sensible, rounded values, usually to one significant figure. Estimates check whether calculated answers are reasonable and give answers when exact data are missing. The result is often given as an order of magnitude, the nearest power of ten.
Useful values to remember:
• mass of an adult: about 70 kg; height: about 1.7 m
• mass of a car: about 1000 kg; walking speed: about 1.5 m s−1
• density of water: about 1000 kg m−3; density of air: about 1.2 kg m−3
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More in Measurements and Uncertainties
- Combining Uncertainties
- Uncertainties from Repeated Readings
- Plotting Graphs
- Error Bars
- Best-fit and Worst-fit Lines
- Uncertainty in a Gradient and Intercept
- Straight-line Graphs y = mx + c
- Logarithmic Graphs
All 12 lessons in Measurements and Uncertainties · All OCR AS-level Physics topics