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After this lesson: You can name the 5 senses off the top of your head NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Les 3 / 10
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Eyes (seeing) Ears (hearing) Nose(smelling) Mouth(tasting) Skin (feeling) inaccurate!! NASK – WAARNEMEN VS METEN Senses
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NASK – OBSERVATION VS MEASURING AND UNCERTAINTY OF MEASUREMENT Our eyes can be fooled Stare at the middle of the disc Les 3 / 10
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This is NOT a video!! NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Our eyes can be fooled Les 3 / 10
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All the brown sections in this picture are equally brown NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Our eyes can be fooled Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT And our skin? Can you, for example, feel with your skin if something is hot or cold? What does the cold water tap feel like after a hot shower? And what does the same cold water tap feel like after cycling in the winter? Is the temperature different then? Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Can we measure time? How many seconds does it take before the traffic lights turn green? start 8 seconds Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT We can measure this, for example, with our body, but not so accurately Which measuring instruments do we use for this? distance ruler, measuring tape time stopwatch, clock temperature thermometer weight scales But are these instruments accurate? Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT How accurate is a stopwatch? Now measure the time of the traffic lights with a stopwatch start 6 seconds Les 3 / 10
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NASK – – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT How accurate is a stopwatch? A number of example measurements AttemptTime (seconds) 16.38 26.39 36.31 46.37 56.35 66.40 76.36 86.41 96.38 106.34 What can you say about this? 1. All the measurements are wrong 2.All the measurements are nearly wrong 3. The measurements are very similar 4. The average is 6.37 5. The written value is pointless Les 3 / 10
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NASK The written value is pointless Measuring seems a lot like shooting at a target The middle is 6 seconds Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Four archers A B C D Who is the winner? Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Four archers A B C D Who is the winner? Who would have won if only the first shot had been fired? Who is better A or B? Who are we? Les 3 / 10
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NASK OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT How accurate is a stopwatch? If I know the correct value, can I revise it AttemptTime (seconds)Correction 16.38 – 0.376.01 26.39 – 0.376.02 36.31 – 0.375.94 46.37 – 0.376.00 56.35 – 0.375.98 66.40 – 0.376.03 76.36 – 0.375.99 86.41 – 0.376.04 96.38 – 0.376.01 106.34 – 0.375.97 average6.376.00 Les 3 / 10
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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Exact C D AccurateExactAccurate ExactAccurateExactAccurate Les 3 / 10
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NASK OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT Assignment Using a stopwatch, measure 10 times the time it takes for light A to change colour. Write these measurements down in a table in your notebook. Determine the average of these measurements Determine the level of inaccuracy Now measure 10 times the time that light B takes to change colour. Write these measurements down in a second table. Determine the level of accuracy Correct the average with the inaccuracy level of A A B 5 seconds ?? How long does traffic light B take? 6.5 seconds Les 3 / 10
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