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St Brendan’s Sixth Form College A Level Physics

St Brendan’s Sixth Form College A Level Physics. James Lawton and Christi Brasher. Welcome to physics. But what is it…. PHYSICS THE STUDY OF EVERYTHING. The range of physics. The very small… To the very large…. Each QUARK in this proton

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St Brendan’s Sixth Form College A Level Physics

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  1. St Brendan’s Sixth Form CollegeA Level Physics James Lawton and Christi Brasher

  2. Welcome to physics • But what is it….

  3. PHYSICS THE STUDY OF EVERYTHING

  4. The range of physics • The very small… • To the very large…..

  5. Each QUARK in this proton is a million million millionth of a metre in diameter! The MILKY WAY galaxy is a thousand million millionmillion meters in diameter! Physicists use standard form to make sense of these extreme numbers.

  6. Standard Form 1/10 = 1x10-1 1/1000 = 1x10-3 0.0000476 = 4.76 x10-5 100 = 1x102 10000 = 1x 104 346000 = 3.46 x 105

  7. Standard Form A million million millionth of a metre 1 x 10-18 m A thousand million millionmillion meters 1 x 1021 m

  8. Unit Prefixes

  9. Precision and uncertainty • A number that represents a physical measurement does more than give a value of quantity. It gives an indication of the precision of the value. • A person measures a coin. Their results are : • (i) 2.4 cm using a ruler • (ii) 2.38 cm using verniercallipers • (iii) 2.377 cm using a micrometer.

  10. Precision and uncertainty • (i) 2.4 cm using a ruler • (ii) 2.38 cm using vernier callipers • (iii) 2.377 cm using a micrometer. • In each case the person measured the coin as accurately as they could. The results show the certainty of the measurement. • The last digit has an implied uncertainty of (+/-) 1

  11. Standard form and precision • What is the volume in m3 of a cube that has sides each of 0.20mm The number 0.20 is precise to 2 significant figures The zero is significant if it does more than just fill the space to the decimal point.

  12. Standard form and precision • What is the volume in m3 of a cube that has sides each of 0.20mm • 0.20mm = 0.20 x10-3m (= 2.0 x10-4m) • (0.2 x10-3)3 = 8.0 x10-12 m3 Notice how the unit changes to m3 8 x10-3 8.0 x10-3 8.00 x10-3

  13. Your turn • What is the area in m2 of a piece of standard A4 paper? 21.0cm x 29.7cm 21.0x10-2m x 29.7x10-2m = 0.06237m2 6.24x 10-2m2 Remember: Standard form Sig figs Units

  14. Precision and uncertainty • A number that represents a physical measurement does more than give a value of quantity. It gives an indication of the precision of the value. • A person measures a coin. Their results are : • (i) 2.4 cm using a ruler • (ii) 2.38 cm using verniercallipers What are the percentage uncertainties above?

  15. Absolute vs Percentage errors 2.4 = 2.4 +/- 0.1 (0.1/2.4) x 100 = 4.166% = 4% (1 sig fig) 2.38 = 2.38 +/- 0.01 (0.01/2.38) x 100 = 0.420% = 0.4% (1 sig fig)

  16. (i) when multiplying and dividing the result has the same number of significant figures as the least precise piece of data. (ii) when adding or subtracting the result has the same number of decimal places as he least precise piece of data. (iii) express the answer to addition and subtraction questions as a value ± the sum of the individual absolute errors. (iv) express the answer to division , multiplication, powers etc as the sum of the percentage errors for each value.

  17. Your turn Calculating volume worksheet.

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