After this lesson:

You can name the 5 senses off the top of your head

NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

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Eyes (seeing)

Ears (hearing)

Nose(smelling)

Mouth(tasting)

Skin (feeling)

inaccurate!!

NASK – WAARNEMEN VS METEN

Senses

NASK – OBSERVATION VS MEASURING AND UNCERTAINTY OF MEASUREMENT

Our eyes can be fooled

Stare at the middle of the disc

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This is NOT a video!!

NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

Our eyes can be fooledLes 3 / 10

All the brown sections in this picture are

equally brown

NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

Our eyes can be fooledLes 3 / 10

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?

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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

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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?

distanceruler, measuring tape

timestopwatch, clock

temperaturethermometer

weightscales

But are these instruments accurate?

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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

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NASK – – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

How accurate is a stopwatch?

A number of example measurements

Attempt Time (seconds)

1 6.38

2 6.39

3 6.31

4 6.37

5 6.35

6 6.40

7 6.36

8 6.41

9 6.38

10 6.34

What can you say about this?

1. All the measurements are wrong

2.All the measurements are nearlywrong

3. The measurements are very similar

4. The average is 6.37 5. The written value is pointless

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NASK The written value is pointless

Measuring seems a lot like shooting at a target

The middle is 6 seconds

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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

Four archers

A B

C D

Who is the winner?

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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?

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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

Attempt Time (seconds) Correction

1 6.38 – 0.37 6.01

2 6.39 – 0.37 6.02

3 6.31 – 0.37 5.94

4 6.37 – 0.37 6.00

5 6.35 – 0.37 5.98

6 6.40 – 0.37 6.03

7 6.36 – 0.37 5.99

8 6.41 – 0.37 6.04

9 6.38 – 0.37 6.01

10 6.34 – 0.37 5.97

average 6.37 6.00

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NASK – OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

Exact

C D

Accurate Exact Accurate

Exact Accurate Exact Accurate

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NASK OBSERVING VS MEASURING AND UNCERTAINTY OF MEASUREMENT

AssignmentUsing 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 B5 seconds ??

How long does traffic light B take?

6.5 seconds

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