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Basic Science - Physics

Basic Science - Physics. Ms Ilana Malan – Semester One 2017. 1. Unit 9 - Graphs. Used for – presenting data Types of graphs and charts include bar/column graph, pie graph, dot plot, histogram, line graph, venn diagram etc Popular graphs in science are mostly line graphs and bar/column graphs.

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Basic Science - Physics

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  1. Basic Science - Physics Ms Ilana Malan – Semester One 2017 1

  2. Unit 9 - Graphs • Used for – presenting data • Types of graphs and charts include bar/column graph, pie graph, dot plot, histogram, line graph, venn diagram etc • Popular graphs in science are mostly line graphs and bar/column graphs

  3. Pie Chart Organisational Chart

  4. Column graph Pictograph

  5. Line Graph

  6. Graph Specifics • Graph Title – Short and descriptive • Axis Title – x-axis for the independent variables - y-axis for the dependent variables - include both measurement and unit - displacement (mm) • Legend – identify if more than one curve on a graph • Data labels – display data labels for data points • Grid lines – vertical and horizontal lines on a graph • Scale – chosen according information • Axis data – proper intervals, include maximum and minimum variable

  7. Graph Title – Short and descriptive Axis Title – x-axis for the independent variables - y-axis for the dependent variables - measurement and unit Legend – identify if more than one curve on a graph Data labels – display data labels for data points Grid lines – vertical and horizontal lines on a graph Scale – chosen according information Axis data – proper intervals, include maximum and minimum variable

  8. Variables Independent: always on x-axis stands alone not dependent on any other variable/measurement Dependent: always on y-axis dependent on independent variable

  9. Interpret a line graph • Cannot see direction on a velocity – time graph • Only readings that can be taken is what is on x- and y-axis • Gradient: always • Gradient on velocity – time graph = acceleration • (+) gradient = acceleration and (–) gradient = deceleration • Area on velocity – time graph = displacement

  10. Gradient 0 s to 5 s = (change in y) ÷ (change in x) = (10 – 0) ÷ (5 – 0) = 10 ÷ 5 = 2 • Gradient 7 s to 10 s = (change in y) ÷ (change in x) = (7 – 10) ÷ (10 – 7) = -3 ÷ 3 = -1

  11. Speed/velocity: 3 m/s means the object move a distance of 3 m in a time of 1 second • Acceleration: means the object’s velocity changes by 3 m/s every second acceleration with a (+) positive sign means that the velocity will increase - acceleration with a (-) negative sign means that the velocity will decrease

  12. Example 1 An object moves from rest and increases its speed to 5 m/s in 5 s. It then turns around and keeps moving at the same speed for the next two seconds. It then accelerates again at for the next 3 seconds. It then slows down over the next 5 seconds to reach a final velocity of 6,5 m/s. Acceleration over last 5 seconds = (v-u) = (6,5 – 14) = - 1,5 m/s2 t 5 a = acceleration ; v = final velocity ; u = initial velocity ; t = time

  13. Example 1 An object moves from rest and increases its speed to 5 m/s in 5 s. It then turns around and keeps moving at the same speed for the next two seconds. It then accelerates again at for the next 3 seconds. It then slows down over the next 5 seconds to reach a final velocity of 6,5 m/s.

  14. Unit 10 – Energy Sources • Non-renewable, formed millions of years ago under conditions that do not exist on earth today. Once they are used up they will not exist any more. Crude oil, natural gas, coal, nuclear. Emit pollution!!! • Renewable, can be used over and over again as long as they are replenished. Include hydro-electric, tidal, wind, wave, geothermal, solar, biofuel. • Saving energy sources – what can I/we do on a daily, monthly, annually basis in order to use less non-renewable sources, cause less pollution, use more energy efficient devices, replenish renewable sources?

  15. Unit 11 – Electricity • AC- alternating current – changes direction of flow • DC – direct current – flow in one direction all the time

  16. Basic circuit symbols

  17. Series • Total resistance = sum of individual resistors • Share the total voltage • Same current in all

  18. Series • Total resistance: 1 kΩ + 2 kΩ + 6 kΩ = 9 kΩ (9 000 Ω) • Share the total voltage: 1 V + 2 V + 6 V = 9 V • V = IR: for R1 = 1 000 Ω x 0,001 A = 1 V for R2 = 2 000 Ω x 0,001 A = 2 V for R3 = 6 000 Ω x 0,001 A = 6 V • Same current in all: 1 mA

  19. Parallel • Total resistance: use formula • All have the same voltage • Current splits up and portion of total current flows in each resistor

  20. Parallel • Total resistance: Now answer still has to be inverted: • All have the same voltage = 12 V • Current splits up and portion of total current flows in each resistor:

  21. Series and Parallel

  22. Series and Parallel

  23. Series and Parallel

  24. Series and Parallel combined resistors

  25. Example 1 Determine the total resistance: 1 Calculate series and parallel separate and 2 Try to combine resistors • 8Ω and 4Ω are in series = 12Ω • These two are in parallel with 12Ω(R4) thus their combined resistance is 6Ω • And this combined 6Ω is again in series with 6Ω (R1) Thus total resistance = 12Ω

  26. Example 1 Total current: I = V ÷ R (total voltage and total resistance) = 12 ÷ 12 = 1 A

  27. Example 2

  28. Example 3 • Total resistance: 15,875 Ω • Total current: I = 0,7559 A • VBC = 6,0472 V • VJK= 4,5354 V • VDI = VEF= VGH= 12 - (VBC+ VJK) = 1,4174 V

  29. Electric current and ammeters • Measure the current flowing through a component • Connected in series, no resistance

  30. Potential Difference and Voltmeter • The voltage measured across a cell/battery indicates the energy given to the charge as it flows through the cell/battery • The voltage measured across a component indicates the energy given out by the charge when current flows through a component • 3 V = 3 J of energy per unit charge

  31. EMF and Potential Difference • EMF is measured by a voltmeter across the cell/battery when no current is flowing, this is the maximum voltage a cell can • Potential Difference is measured by a voltmeter across the cell/battery with current flowing, this is lower than emf as a result of internal resistance within the cell/battery • Formula: V = IR

  32. EMF and Potential Difference

  33. Battery: Series vs Parallel

  34. Example 1

  35. Example 2 • All resistors are in series thus total resistance = 10 + 20 + 30 = 60 Ω • Use the formula V = IR to determine current • I = V ÷ R = 12 ÷ 60 = 0,2 A

  36. Example 3 • Determine the total current

  37. Wire a plug

  38. Unit 12 - Radioactivity • Atom: same number of electrons and protons (neutral) • Ion: electrons are more/less than protons (has a charge) • Negative ion: results when electrons are gained (- charge) • Positive ion: results when electrons are lost (+ charge) • Isotope: same element, same number of protons, different number of neutrons in the nucleus

  39. Isotopes

  40. Radioactivity

  41. Uses of radioactivity

  42. Unit 13 - Forces • Forces: pulling (in front of object) or pushing (behind object) • Forces can: change velocity of object, make object move, make object stop, change direction of object, change shape of object • Is a vector: has both magnitude and direction

  43. Resultant Force • A resultant force is: A single force that represents or has the same effect as two or more forces acting on the same object at the same time • Upward and North and to the right forces are given (+) sign • Downward and South and to the left forces are given (-) sign • During the calculation of the resultant force these signs are used • Add all the forces acting on the object • The sign of the answer indicates the direction of the resultant force

  44. Resultant Force

  45. Example 1

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