Transcript
WHAT IS PHYSICS?
From Greek word ‘physikos’
IS A BRANCH OF SCIENCE CONCERNING THE STUDY ABOUT NATURAL
PHENOMENA AND PROPERTIES OF MATTER
HAVE YOU EVER WONDER?
Why hot coffee will gradually turn cold
after an hour?
How your image can be formed on
mirror?
Forces and
pressure
Electric and
Electronic
Wave
Electromagnetism
Physical quantityIs a quantity that can be measuredEg: mass, length, volume, temperature
Base quantity Derived quantity
Is a quantity that cannot be derived in other base quantity.
Is a quantity that can be derived from other base quantity by multiplication or division.
Base Quantity SI unitsLength, l metres, mMass, m kilogram,
kg
Time, t second, sTemperature, T Kelvin, k Electrical current, I Ampere, A
Derived Quantity Units
Volume, V m3
Density, kgm-3
Velocity, v ms-1
Force, F N
Acceleration, a ms-2
Base quantity Derived quantity
Prefixes Use to represent physical quantities which
are very big or very small in S.I units.Prefix Symb
olMultiplication
factorValue
Tera T × 1012 1 000 000 000 000
Giga G × 109 1 000 000 000Mega M × 106 1 000 000Kilo k × 103 1000Deci d × 10-1 0.1Centi c × 10-2 0.01Milli m × 10-3 0.001Micro × 10-6 0.000001Nano n × 10-9 0.000000001Pico p × 10-12 0.000000000001
Scientific notation/ Standard form
Numerical values which very small or big can be written in standard form:
A × 10n
(1 ≤ A < 10, positive or negative integer)Exercises:1)Write 0.0000008 in scientific notation.2)The equatorial diameter of earth is 12 760
000 m. Write the diameter in standard form.
Conversion unitConvert the measurement:a)5.7 cm to metre
b)1.5 km to metre
c)1.1 g cm-3 to kg m-3
d)1.45 × 10-2 Mm to m
e)2.25 × 1010 μm to m
f)2.2 × 108 Gm to m
g)36 kmh-1 to ms-1
h)8 cm2 to km2
i) 16 m2 to cm2
j) 8.1 kgm-3 to gcm-3
k)25 ms-1 to kmh-1
1.3.1 Measure physical quantity using appropriate instruments.
a) Metre rule
Function Sensitivity
Measure length from a few cm up to 1m
0.1 cm
b) Thermometer
Function Sensitivity
Measure temperature. 1oC / 2oC
c) Stopwatch
Function Sensitivity
Measure time intervals. 0.1 s to 0.2 s
d) Ammeter
Function Sensitivity
Measure electric current. 0.1 A / 0.2 A
e) Voltmeter
Function Sensitivity
Measure potential difference / voltage.
0.1 V / 0.2 V
f)Measuring tape
Function Sensitivity
Measure long distance, circumference of round
object.
1.0 cm
g) Vernier callipers
Function Sensitivity
Measure length, diameter inner and outer and depth object with dimension up
to 12.0 cm.
0.01 cm
Function
Main scale Scale of 0.1 cm to 12 cm
Inside jaws Measure internal diameter
Outside jaws Measure external diameter and length
Tail Measure depth
How to take reading of vernier callipers?1. Read main scale reading Observe the zero mark ‘0’ on vernier scale. The vernier scale lies between 1.2 cm and 1.3 cm. Reading on main scale is 1.2 cm.2. Read vernier scale reading Read mark on vernier scale that is exactly in line
with any mark on main scale. Reading on vernier scale= 0.03 cm
Reading = Reading on + Reading on main scale vernier scale
= 1.2 + 0.03 cm = 1.23 cm
Main scale
Vernier scale
h) Micrometer Screw Gauge
Function Sensitivity
Measure thickness or diameter of small object in range between 0.10 mm
and 25.00 mm.
0.01 mm or 0.001 cm
Function
Anvil and spindle Used to grip object.
Sleeve Main scale
Thimble Thimble scale
Ratchet knob Used to prevent exceeding pressure
1. Read main scale reading Read main scale at edge of thimble Reading main scale = 5.5 mm2. Read thimble scale reading Thimble scale reading = 0.28 mm
How to take reading of micrometer screw gauge?
Reading = Main scale + Thimble scale
= 5.5 + 0.28 = 5.78 mm
The smaller the change which can be measured by instrument, the more sensitive the instrument is.
The smallest scale division on measuring instruments is the more sensitive the instrument is.
Different measuring instruments have different levels of sensitivity.
1.3.2 Explain SensitivitySensitivity of an instruments is its
ability to detect small change in the quantity to be measured.
Which one is more sensitive?
1.3.2 Explain Accuracy and Consistency
ACCURACY CONSISTENCY
Is how close the value of the measurement to the actual value.
Ability to register the same reading.
Consistence Inconsistence
Accurate
Inaccurate
ACCURACY CONSISTENCYHow to improve accuracy:1.Repeat the experiment and take average reading.2.Avoid zero error.3.Avoid parallax error.4.Use measuring instrument with high sensitivity.
How to improve consistency:1.Avoid parallax error.
Consistence but not accurate
Accurate but inconsistence
Inaccurate and Inconsistence
Accurate and consistence
SYSTEMATIC ERROR RANDOM ERROR
1. Zero error Incorrect position of zero
point of measuring instrument.
2. Incorrect calibration Error in calibration of
instrument which makes the instrument defective.
- Systematic error will lead to decrease in accuracy.
1. Parallax error error because of the
observers eyes.2. Natural error change in temperature,
humidity etc when experiment in progress
3. Wrong technique apply excessive pressure.
- Random error will lead to decrease in consistency.
How to reduce systematic error:Correct reading = reading obtained - zero error
How to reduce random error: Repeat the experiment and take average reading.
1.3.3 Explain Types of Experimental Error
Zero error
Parallax error
How to eliminate zero error?
Micrometer Screw Gauge
Negative zero error
Zero error= -0.04 mm
Positive zero error
Zero error= 0.02 mm
Vernier Callipers
No zero error
Negative zero error
Positive zero error
zero error = 0.04 cm
zero error = -0.02 cm
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