#### Fractions 2

An approach to adding and subtracting fractions, using an understanding of the processes involved.

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Mutiplying and dividing fractions: a systematic approach to this perennial problem.

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A presentation showing both the ideas about centripetal force and a simple classroom method of checking the way in which this force is related to mass, speed and radius.

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A look at what was known when Newton started to develop his theory of gravitation and how he used these ideas and data to make his great forward step

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#### Measuring the speed of pulses

A short clip showing the experimental measurement of the speed of electrical pulses in a cable - a large fraction of the speed of light.

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A presentation showing how to measure the speed of sound over a short distance on a laboratory table.

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A short clip showing the measurement of the speed of sound over short distances.

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The concept of oxidation and reduction is explained and generalised using oxidation numbers with ionic and covalent examples. Several equations are balanced, using the oxidation number method to fix various atomic ratios.

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Real-life story about one of the first uses of penicillin. An interview with a survivor.

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Making life easy when using percentages. A sometimes fraught topic looked at differently.

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