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
a = acceleration ; v = final velocity ; u = initial velocity ; t = time
Time 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
velocity
12,5
9,5
6,5

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 = Ω x 0,001 A = 1 V
for R2 = Ω x 0,001 A = 2 V
for R3 = 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 = (VBC + VJK)
= 1,4174 V

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

31. 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

34. 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

35. EMF and Potential Difference

36. Battery: Series vs Parallel

37. Example 1

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

39. Example 3
Determine the total current

40. Wire a plug

41. 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

42. Isotopes

44. Radioactivity

45. Uses of radioactivity

47. 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

48. 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

49. Resultant Force

50. Example 1

51. Example 2 2 N south ; 3 N North ; 6 N North ; 8 N south
Determine all the forces in the same direction first:
2 N + 8 N (both south) = 10 N south
3 N + 6 N (both north) = 9 N north
Thus the resultant force is: – 10 (force is south) + 9 (force is north)
= - 1 N [the (-) sign indicating the
direction of the resultant force is south]

52. Unit 14 Sound
Sound is produced when an object vibrates, causing small but rapid changes to the air pressure around it
When layers of air molecules are pushed close together, a compression of air particles is formed
When the layers are pulled apart a decompression or rarefaction of the air molecules is formed

53. Production of Sound

54. Production of Sound

55. Type of Wave

56. Wave Properties
Wavelength: the distance between one point on the wave and the equivalent next point of the same wave

57. Wave Properties
Maximum displacement/maximum distance a wave moves from its resting position

58. Wave Properties
Period (T): time taken for one complete wave (time for one wavelength)
Frequency (f): number of waves passing a point in one second, calculate with 1 ÷ T

59. Loudness of sound
Determined by the amplitude of a wave

60. Pitch of sound
Determined by the frequency of a wave

61. Calculations

62. Example 1 Speed/velocity of the wave is 200 m/s
Wavelength of the wave is 2 m
Period of the wave is wavelength ÷ velocity = 2 ÷ 200 = 0,01 s
Frequency of the wave is 1 ÷ 0,01 = 100 Hz

63. Example 2 Period of the wave is 4 seconds
Frequency of the wave is 1 ÷ 4 = 0,25 Hz

64. Example 3

65. Example 4
Sitting on a beach an observer with a stopwatch takes the time every time a wave reaches the beach. He can see that in 3,5 minutes 3 waves reaches the beach. If the distance between successive wave crests is 11 m, determine the speed at which the waves move.
Hint, you would need period/freqeuncy

66. Thank You.