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# Introduction to physics

## on Jan 14, 2012

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## Introduction to physicsPresentation 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 quantity
• Is a quantity that can be measured
• Eg: 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 Derived quantity Base Quantity SI units Length, l metres, m Mass, m kilogram, kg Time, t second, s Temperature, T Kelvin, k Electrical current, I Ampere, A Derived Quantity Units Volume, V m 3 Density,  kgm -3 Velocity, v ms -1 Force, F N Acceleration, a ms -2
• Prefixes
• Use to represent physical quantities which are very big or very small in S.I units .
Prefix Symbol Multiplication factor Value Tera T × 10 12 1 000 000 000 000 Giga G × 10 9 1 000 000 000 Mega M × 10 6 1 000 000 Kilo k × 10 3 1000 Deci d × 10 -1 0.1 Centi c × 10 -2 0.01 Milli m × 10 -3 0.001 Micro  × 10 -6 0.000001 Nano n × 10 -9 0.000000001 Pico p × 10 -12 0.000000000001
• Scientific notation/ Standard form
• Numerical values which very small or big can be written in standard form:
• A × 10 n
• (1 ≤ A < 10, positive or negative integer)
• Exercises:
• Write 0.0000008 in scientific notation.
• The equatorial diameter of earth is 12 760 000 m. Write the diameter in standard form.
• Conversion unit
• Convert the measurement:
• 5.7 cm to metre
• 1.5 km to metre
• 1.1 g cm -3 to kg m -3
• 1.45 × 10 -2 Mm to m
• 2.25 × 10 10 μ m to m
• 2.2 × 10 8 Gm to m
• 36 kmh -1 to ms -1
• 8 cm 2 to km 2
• 16 m 2 to cm 2
• 8.1 kgm -3 to gcm -3
• 25 ms -1 to kmh -1
•
• 1.3.1 Measure physical quantity using appropriate instruments.
• a) Metre rule
b) Thermometer c) Stopwatch Function Sensitivity Measure length from a few cm up to 1m 0.1 cm Function Sensitivity Measure temperature. 1 o C / 2 o C Function Sensitivity Measure time intervals. 0.1 s to 0.2 s
• d) Ammeter
e) Voltmeter f) Measuring tape Function Sensitivity Measure electric current. 0.1 A / 0.2 A Function Sensitivity Measure potential difference / voltage. 0.1 V / 0.2 V 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?
• 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.
• Read mark on vernier scale that is exactly in line with any mark on main scale.
• Reading on vernier scale= 0.03 cm
• = 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
• Read main scale at edge of thimble
• Reading main scale = 5.5 mm
• 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 Sensitivity Sensitivity 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 Accurate Inaccurate ACCURACY CONSISTENCY Is how close the value of the measurement to the actual value. Ability to register the same reading. Consistence Inconsistence
• ACCURACY CONSISTENCY
• How to improve accuracy:
• Repeat the experiment and take average reading.
• Avoid zero error.
• Avoid parallax error.
• Use measuring instrument with high sensitivity.
• How to improve consistency:
• Avoid parallax error.
• Consistence but not accurate
• Accurate but inconsistence
• Inaccurate and Inconsistence
• Accurate and consistence
• 1.3.3 Explain Types of Experimental Error SYSTEMATIC ERROR RANDOM ERROR
• Zero error
• Incorrect position of zero point of measuring instrument.
• Incorrect calibration
• Error in calibration of instrument which makes the instrument defective.
• - Systematic error will lead to decrease in accuracy .
• Parallax error
• error because of the observers eyes.
• Natural error
• change in temperature, humidity etc when experiment in progress
• 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.
• 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