Starter quiz
- Match the following quantities to their units.
- distance⇔metres (m) ✓
- time⇔seconds (s) ✓
- speed⇔metres per second (m/s) ✓
- Which of the following is the correct equation for speed?
- speed = distance x time
- speed = distance + time
- speed = distance – time
- speed = distance ÷ time ✓
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- Which of the following is not a unit of speed?
- metres per second (m/s)
- metres per second squared (m/s²) ✓
- kilometres per second (km/s)
- miles per hour (mph)
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- Sam take three repeat measurements for the time taken for a wave to travel a set distance. The results are 0.21 s, 0.19 s and 0.26 s. Calculate the mean time. You do not need to include the units.
- '0.22' ✓
- What effect do random errors have on repeat readings?
- Random errors make repeat readings identical.
- Random errors make repeat readings slightly different to each other. ✓
- Random errors make repeat readings more accurate.
- Random errors make all repeat readings inaccurate by the same amount.
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- The uncertainty in a measured value refers to ...
- the accuracy of the result.
- the validity of the result.
- the amount of doubt about the result. ✓
- the amount of certainty about the result
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Exit quiz
- Which of the following are SI (International System of Units) units of distance and time?
- metre ✓
- second ✓
- mile
- hour
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- Which of the following is the SI unit of speed?
- metres per second ✓
- kilometres per hour
- miles per hour
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- Which of the following affects the speed of a water wave?
- the type of water (i.e. how much salt it contains) ✓
- the shape of the water wave
- the number of waves per second
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- Why are repeat measurements taken when measuring the time it takes a water wave to travel a set distance?
- errors can be identified and discounted or repeated ✓
- reaction times improve with practice
- mistakes are often made with the first measurement
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- What is the name given to the type of error caused by differences in a person’s reaction time?
- predictable
- random ✓
- systematic
- human
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- A result that is close to the true or expected value is ______.
- 'accurate' ✓
Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- The speed of water waves can be measured using measurements of distance travelled and time taken.
- Random errors are made when the method limits how accurate a measurement can be.
- The effect of random errors can be reduced by repeating readings and calculating a mean.
- The uncertainty in a mean result is calculated from half the range of the repeat measurements.
Common misconception
Calculating a mean of repeat readings reduces (random) errors in measurements.
Calculating a mean reduces the effect that random errors have on a final result. The random errors in the original readings are unaffected.
Keywords
Random error - A random error is caused by unpredictable factors that affect the measurement of a variable.
Uncertainty - Uncertainty is an estimate of how far from the true value a measurement might be. It is equal to half the range of repeat measurements.
Mean - The mean is calculated by adding each measurement and dividing by the number of measurements.
Anomalous result - An anomalous result is a measurement that is significantly different from the others. It should be crossed out and not used in calculating the mean.
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