1. What is Physics?

2. What is Physics?

3. Feb 28, 2009 Merlion hit by lightning
A lightning bolt struck the Merlion statue at about 4.30pm yesterday.
The national icon at One Fullerton facing the Singapore River
lost part of its top left mane and is believed to have its right ear chipped.
About 20 to 30 people nearby, including tourists, ran helter-skelter in the pouring rain when debris from the Merlion's head went flying.
Some ran to safety in the nearby shops and cafes.
The fragments fell onto the patio at One Fullerton and the Singapore River Cruise counter near the Merlion.
Nobody was hurt.
Eyewitness Ms Rina Toh, 17, a barista at The Coffee Bean and Tea Leaf at One Fullerton, said: 'I saw a bright Z-shaped lightning bolt, and it was a lot bigger than usual.'
She was standing at the counter and could see the Merlion.

4. What is Physics?
Physics is the study of the natural world around us – from the very large, such as the solar system, to the very small, such as the atom.

5. Physical Quantities, SI Units and Measurement
In the quest to understand nature, scientists use physical quantities to describe the world around us.
Physical Quantities, SI Units and Measurement
Chapter 1

6. At the end of this chapter…
You should be able to:
show understanding that all physical quantities consist of a numerical magnitude and a unit
recall the following base quantities and their units: mass (kg), length (m), time (s), current (A), temperature (K)
use the following prefixes and their symbols to indicate decimal sub-multiples and multiples of the SI units: nano (n), micro (μ), milli (m), centi (c), deci (d), kilo (k), mega (M)

7. At the end of this chapter…
You should be able to:
show an understanding of the orders of magnitude of the sizes of common objects ranging from a typical atom to the Earth
describe how to measure a variety of lengths with appropriate accuracy by means of tapes, rules, micrometers and calipers, using a vernier scale as necessary
describe how to measure a short interval of time including the period of a simple pendulum with appropriate accuracy using stopwatches or appropriate instruments

8. Cubit

9. Why do We Need to Measure Things?
Let’s do this as a class…
Work in groups of two
Compare the length between the elbow to the first finger tip.

10. Why do We Need to Measure Things?
Are they the same?

11. Physical Quantities and SI Units
Base Quantity
Name of SI unit
Symbol for SI Unit
Length
metre m
Mass
kilogram kg
Time
second s
Electric Current
ampere A
Temperature
kelvin K
Intensity
candela cd
Amount of Substance
mole
mol

12. Physical Quantities
A physical quantity when measured may be described in terms of
A number
Its unit of measurement
actual length = m

13. Physical Quantities
What is your height?
2 m
quantity
unit

14. Physical Quantities
Mass – unit of measurement, kilogram (kg)

15. Physical Quantities
Time – unit of measurement, second (s)

16. Physical Quantities
What are some problems we might face in our daily lives if there are no standard measurements?

17. Do You Know??? 1 400 000 000 m 1.4 Gm (gigametre) 0.0002 m
Diameter of the Sun
Thickness of a strand of hair m m
1.4 Gm (gigametre)
0.2 mm (millimetre)

18. Prefixes for SI units 10 giga- G 10 mega- M 10 kilo- k 10 deci- d 10
Factor
Prefix
Symbol 10 9
giga- G 10 6
mega- M 10 3
kilo- k 10 - 1
deci- d 10 - 2
centi- c 10 - 3
milli- m 10 - 6
micro- 10 - 9
nano- n

19. Prefixes Exercise 1 Express the following quantities
in their respective SI unit.
One kilometer =
1000m or 103m
One microsecond =
s or 10-6s
One centimeter =
0.01m or 10-2m
One gram =
0.001kg or 10-3kg
Factor
Prefix
Symbol
109
giga- G
106
mega- M
103
kilo- k
10-1
deci- d
10-2
centi- c
10-3
milli- m
10-6
micro-
10-9
nano- n

20. Prefixes Exercise 1 One miligram = 0.001g or 10-3g =10-6 kg
Factor
Prefix
Symbol
109
giga- G
106
mega- M
103
kilo- k
10-1
deci- d
10-2
centi- c
10-3
milli- m
10-6
micro-
10-9
nano- n
One miligram =
0.001g or 10-3g
=10-6 kg
One millisecond =
0.001s or 10-3s
One minute =
60s
One hour =
3600s

21. What does SI units mean? Système International
International System of Units

22. Measurement of Length m metre
The SI unit for length is ( )
Other units for length: m
metre
millimetre (mm), centimetre (cm), kilometre (km)

23. Accuracy of Instruments
Measurement of Length
Range
Suitable Instruments
Accuracy of Instruments
Several metres (m)
Several centimetres (cm)
Between 1cm to 10cm
Less than 2 cm
Measuring
Tape
0.1 cm
(or 1 mm)
Metre/Half-
metre Rule
0.1 cm
(or 1 mm)
Vernier
Calipers
0.01 cm
(or 0.1 mm)
Micrometer
Screw Gauge
0.001 cm
(or 0.01 mm)

24. Measurement of Length Metre rule: Measuring Tape
- Length of classroom, car, corridor
Metre rule:
Length of desk, book

25. Measurement of Length Parallax Error What is Parallax Error?
It is the error which arises due to incorrect positioning of the eye.
2.7 cm
correct
3.0 cm
wrong cm 1 2 3

26. Measurement of Length Parallax Error How do we avoid Parallax Error?
Always place the eye vertically above the mark being read. OR
Place the eye in level with the mark being read.
3.0 cm
wrong
2.7 cm
correct cm 1 2 3

27. Vernier Calipers French scientist Pierre Vernier(1580-1637)
Accuracy: 0.01 cm (or 0.1 mm)

28. How to read off the Vernier Caliper?
11mm
0.7mm mm
Measured Value
Reading = 11 mm mm = 11.7 mm

29. Vernier Calipers Its structure and its application
The inside jaws is used to measure internal diameter of test-tube, ring etc.
In main scale, reading = 1.90 cm
in vernier scale, reading = 0.01 cm
the actual reading = 1.91 cm

30. Vernier Calipers Its structure and its application
The outside jaws is used to measure small length, diameter of test-tube etc.
main scale reading = 4.20 cm
vernier scale reading = 0.06 cm
Actual reading = 4.26 cm

31. Exercise 1 mm
Reading = 19 mm mm = 19.4 mm

32. Exercise 2 mm
Reading = 4 mm mm = 4.7 mm

33. Exercise 3

34. Exercise 4

35. Exercise 5 mm
Reading = 12 mm mm = 12.6 mm

36. Exercise 6 mm
Reading = 7 mm mm = 7.5 mm

37. http://www.superteachertools.com/millionaire/onlin e/game2013.php

38. vernier scale (movable)
Vernier Calipers
Zero Error (Vernier Calipers)
Positive Zero Error 10 5
main scale (fixed)
vernier scale (movable)
0.1mm
+0.1 mm
Zero Error = mm
If the observed reading = 32.4mm, then
Actual measurement = Observed reading – Zero error
= mm
= cm
+0.1
(+0.1)
32.3

39. vernier scale (movable)
Vernier Calipers
Zero Error (Vernier Calipers)
Negative Zero Error 10
main scale (fixed)
0.1mm
vernier scale (movable) 5 10
- 0.2 mm
Zero Error = mm
If the observed reading = 32.4 mm, then
Actual measurement = Observed reading – Zero error
= mm
= mm
- 0.2
(-0.2)
32.6

40. Micrometer Screw Gauge
Accuracy: cm (or 0.01 mm)
Smaller length, such as diameter of thin wire, thickness of a piece of paper etc can be measured by micrometer screw gauge.

41. Micrometer Screw Gauge
3 mm
0.09 mm
Sleeve reading = mm
Thimble reading= mm
Reading = mm
Reading = cm
3.0
0.09
3.09
0.309

42. Micrometer Screw Gauge
0.30 mm
5.5 mm
Sleeve reading = mm
Thimble reading= mm
Reading = mm
Reading = cm
5.5
0.30
5.80
0.580

43. Micrometer Screw Gauge
0.06 mm
3.5 mm
Sleeve reading = mm
Thimble reading= mm
Reading = mm
Reading = cm
3.5
0.06
3.56
0.356

44. Exercise 1
11.5mm
0.25mm
Reading = 11.5 mm mm = mm

45. Exercise 2 15 20 30 25
Reading = 20.5 mm mm = mm

46. Micrometer Screw Gauge
Zero Error (Micrometer Screw Gauge)
Positive Zero Error
+0.02 mm
Zero Error = mm
If the observed reading = 2.37mm, then
Actual measurement = Observed reading – Zero error
= mm
= mm
+0.02
(+0.02)
2.35

47. Micrometer Screw Gauge
Zero Error (Micrometer Screw Gauge)
Negative Zero Error mm
Zero Error = mm
If the observed reading = 2.37mm, then
Actual measurement = Observed reading – Zero error
= mm
= mm
- 0.03
(- 0.03)
2.40

48. Measurement of Time Two types: SI unit of time: second, s
Stopwatches are used to measure short intervals of time.
Two types:
Digital stopwatch
Analogue stopwatch
SI unit of time: second, s

49. Accuracy of Instruments
Measurement of Time
Instruments
Usage
Accuracy of Instruments
Watch/Clock
hrs, mins, sec
Analogue Stopwatch
mins, sec
Digital Stopwatch
Atomic Clock
about s -
Pendulum Clock
Radioactive decay clock
thousand of years
1 s
0.1 s
0.01 s

50. Measurement of Time Watch/Clock
used for measuring long intervals of time
most modern watches depend on the vibration of quartz crystals to keep time accurately
the energy that keeps these crystals vibrating comes from a small battery
many watches still make use of coiled springs to supply the needed energy

51. Measurement of Time Stopwatch (Analogue/Digital) Digital Stopwatch
A stopwatch is used to measure short intervals of time.
stopwatches (analogue and digital)
Digital Stopwatch
accuracy = 0.01 s
Analogue Stopwatch
accuracy = 0.1 s

52. Measurement of Time Atomic Clock
Atomic clock also work on oscillation.
The big difference between a standard clock in your home and an atomic clock is that the oscillation in an atomic clock is between the nucleus of an atom and the surrounding electrons.
They even keep time better than the rotation of the Earth and the movement of the stars.
Without atomic clocks, GPS navigation would be impossible, the Internet would not synchronize, and the position of the planets would not be known with enough accuracy for space probes and landers to be launched and monitored.

53. Measurement of Time Pendulum Clock
clocks make use of a process which is a regularly repeating motion (oscillations), such as the swing of a pendulum
such oscillations are very regular so period is regular
most modern clocks depend on the vibration of quartz crystals to keep time accurately
in clocks that are wound up, elastic potential energy is stored in coiled springs

54. What is a pendulum?
A small object suspended by a piece of string or tread is called a simple pendulum.
The distance from the centre of the pendulum bob to the point of suspension is called the length of the pendulum.
One complete to and fro movement of the pendulum is called an oscillation.
The time taken for one complete oscillation is called the period.
The distance between the rest position of the pendulum and the extreme point of its oscillation is called the amplitude.

55. Diagram of a Pendulum Amplitude Length of Pendulum From B to C A C B
Oscillation
From A to B to C
and back to B to A

57. Finding the Period of a Pendulum
To find the period:
1. Take the total time for 20 oscillations.
Why 20?
2. Repeat 2 more times.
3. Calculate the average time for 20 oscillations.
4. Divide by 20 to obtain the period.

58. What Affects the Period of a Pendulum?
Mass?
Amplitude?
Length?

59. Simple Pendulum When the length increases, the period increases.
When the length decreases, the period decreases.
When the mass of the bob increases/decreases, there is no effect on the period.

60. Simple Pendulum
When the amplitude of the bob increases/decreases, there is no effect on the period.
When the same experiment is done on the moon, the period increases.

61. Pendulum Exercise
The time taken for a pendulum to swing from rest position A to B is 0.8s. What is the time taken for the pendulum to make 20 oscillations?