GENERAL PHYSICS

CHAPTER 1: GENERAL PHYSICSPhysical Quantities and Units 1.1 Physical Quantities 1.2 SI Units 1.3 The Avogadro constant 1.4 Scalars and vectors2. Measurement Technique 2.1 Measurements 2.2 Errors and uncertainties

11.1 Physical QuantitiesPhysical quantity is one that can be measured and consist of a magnitude and unit.In fact, we used physical quantities to observe and measure something.For example: length, mass, time, weight, electric current, force and velocity.Classified into 2 types: Base quantity- physical quantities that cannot be defined in terms of other quantities.Derived quantity combination of different base quantities

21.2 SI unitsSI Units International System of UnitsIn SI, prefixes are attached: used to denote very big or very small numbers.

PrefixValueStandard FormSymbolTera1 000 000 000 0001012TGiga1 000 000 000109GMega1 000 000106MKilo1 000103kDeci0.110-1dCenti0.0110-2cMilli0.00110-3mMicro0.000 00110-6Nano0.000 000 00110-9nPiko0.000 000 000 00110-12p3Base QuantitiesBase QuantitiesSI UnitSymbolLength , lMetermMass, mKilogramkgTime, tSecondsTemperature, TKelvinKElectric current, IAmpereA4Derived QuantitiesDerived QuantitySymbolRelationship with base quantityDerived unitAreaALength X Lengthm2VolumeVLength X Length X Lengthm3DensityMass / Length X Length X LengthKg m-3VelocityvLength / Timem s-1AccelerationVelocity / Timem s-2MomentumpMass X Velocitykg ms-1PressurePDaya / LuasKg m-1 s-2 or N m-2 or Pascal (Pa) 5

678Exercise 2 (SCP 131)91011121318. Pressure is defined asA force per unit area C force per unit lenghtB mass per unit volume

Which of the followings is equal to 1 second?A 10 msC 1000 msB 100 msD 10 000 ms

20. Which of the followings pair is true?A Force JouleB Frequency -per secondC Work wattD Electrical charge - ampere141.3 The Avogadro Constant1516171.4 Scalars and vectors1819

Sum of vectorsSum of the vectors is another vector known as the resultant vector, P+QSum of vector follows the following rules: a) commutative rule : P+Q=Q+P b) associative rule : (P+Q)+R =P+(Q+R) c) distributive rule : m(P+Q) = mP+mQTwo method to find resultant vector : a) Parallelogram of vectors b) Triangle of vectors

20Parallelogram of vectors- The two vectors P and Q are represented by the adjacent sides AB and AD of parallelogram. The line DC is drawn parallel to AB and BC is drawn parallel to AD to complete the parallelogram ABCD. The resultant vector (P+Q) is represented by the diagonal AC in magnitude and direction.

21

Triangle of vectors-The line AB is drawn to represent the vector P in magnitude and direction. From B, the line BC is drawn to represent the vector Q. The resultant (P+Q) is represented by the line AC in magnitude and direction.

22

Subtraction of vectorsthe subtraction of two vectors P and Q can be written as the sum of two vectors. P- Q = P +(-Q)

23

Resolving a vectorA vector R may be considered as the sum of two vectors.A vector has only one pair of components, which are mutually perpendicular to each other as follow:24

25

26

2728293031322.Measurement Techniques2.1 MeasurementLengthMeasuring tape is used to measure relatively long lengthsFor shorter length, meter rule or a shorter rule will be more accurate

33

Vernier CalipersConsist of two scales which are main scale and vernier scale.Allows measurements up to 0.01cmConsists of a 0.9cm long scale divided into 10 divisions34

Method of reading the Vernier CallipersObserve the zero mark 0 on the vernier scale.Then write down the value of the reading on the main scale before or exactly touching the0 mark on the vernier scale,i.e 3.1 cm in Figure above.Hence, the reading = Reading on the main scale + Reading on the vernier scale = 3.1 + 0.08 =3.18 cm

35Micrometer Screw GaugeTo measure diameter of fine wires, thickness of paper and small lengthsTwo scales : main scale and circular scale

36

Taking the reading on the Micrometer Screw gauge

=Reading on the sleeve + Reading on the scale of the thimble=7.00 mm+0.28 mm= 7.28 mm37

Timemeasured in years, months, weeks, minutes and seconds.SI unit for time is the second (s).StopwatchMeasure short intervals of timeTwo types: digital stopwatch, analogues stopwatchDigital stop watch more accurate as it can measure time in intervals of 0.01 seconds.Analogue stopwatch measures time in intervals of 0.1 seconds.38

39

The table below show the range and precision of some measuring instruments

40InstrumentRange of measurementAccuracyMeasuring tape0-5m0.1 cmMetre rule0-1m0.1cmVernier calipers0-15cm0.01cmMicrometer screw gauge0-2.5cm0.01mm2.2 Errors and uncertainties41ii) Random errors - Main source is the observer. - Example of random error is parallax errors

- Can be reduced by taking repeated readings - The mean/ average is the best estimate of the true value,.42

ReferencesJ.S Walker (2011) Physics. Pearson Custom Publishing J.S Walker (2011) Principles of Physics. 9th Ed. Wiley M. Crundell: AS/A-Level Physics Essential Word Dictionary: Philip Allan Updates, 2001. J.D Wilson, A.J Buffa, B.Lou (2011) College Physics. 6th Ed. Pearson Prentice Hall

43Range and GradeMarksGradePointer85 - 100A4.0080 84A-3.7075 79B+3.3070 74B3.0060 69B-2.7055 - 59C+2.3050- 54C2.0045 49C-1.7040 44D+1.3035 39D1.0030 34E0.670 29F0.00FXXTidak hadir peperiksaan tanpa kebenaranDengan kebenaranTLTidak lengkap dan diberi tempoh dengan kebenaran DekanDKGugur Subjek Dengan KebenaranR1Ulang 1 dan seterusnyaP/GLulus/GagalEXDikecualikan44