Mind Map Gallery chapter-1-physical-quantities-units-and-measurements
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Edited at 2020-10-09 06:00:57
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Chapter 1: Physical Quantities, Units and Measurements
Periodic Motion
Many things around us move in a manner thatrepeats itself.
Eg. Stand fan which switched on, air -conditioner outlets, frequency of the bus 972,etc.
In science, it is more convenient to use thependulum to study this repeated motion.
Pendulum
A simple pendulum consists of a bob (smallweight) swinging back and forth on a string.
Oscillation
A full oscillation occurs when there is acomplete to and fro motion of the bobfrom A➜B➜C➜B➜A.
Period
It is defined as the time taken for one full fulloscillation to occur.
Frequency
It is defined as the number of completeoscillation in 1 second.
Ticker tape timer
A ticker tape timer is an electrically operateddevice that marks very short intervals of timeonto a tape in the form of dots.
The time is connected to an electricity supplyand cause the metal strip attached to thetimer to vibrate. Eg: 50 Hz or 50 times everysecond.
The time interval between two consecutive dotsis 1/50 s = 0.02s.
Frequency of Ticker Tape: No of dots producedin a second.
Hence, the ticker tape timer is a kind of clockthat measures time in 0.02s intervals.
When distance between successive dots isconstant, the tape is moving at a constantspeed.
When distance between successive dotsincreases, the tape is moving faster (speedincrease).
When distance between successive dotsdecreases, the tape is moving slower (speeddecreases).
Measurement Of Time
SI Unit: Second
Symbol: s
Instruments Used:
Clocks
Degree of Accuracy: 1 Second
Stopwatches
Degree of Accuracy: 0.01 second (Digital), 0.1second (Analog)
Ticker-tape Timer
Degree of Accuracy: 0.02 seconds between 2dots
Measurement of Length
SI Unit: Metres
Symbol: m
* The type of instrument used to measurelength depends on the length to be measuredand the accuracy required. Accuracy is thesmallest unit an instrument can measure.
Instruments
Measuring Tape
Measured Length Range: 0m 10m
Accuracy: 0.1cm or 1 mm
Metre Rule
Measured Length Range: 0cm to 100cm
Accuracy: 0.1 to 1 mm
Vernier Calipers
Measured Length Range: 2cm to 10cm or20mm to 100mm
Accuracy: 0.01cm or 0.1mm
Micrometer Screw Gauge
Measured Length Range: Less than 3 cm or0mm to 30mm
Accuracy: 0.001cm or 0.01mm
Rulers
Accuracy: 0.1cm or 1mm
Parallax Error
The incorrect way of reading from a ruler leadsto it
How to prevent it?
When taking the measurement on a ruler. placethe eye directly above the scale.
Take several readings, and then take theaverage.
+More on Vernier Caliper
Zero Errors
Positive
Before any measurement is made, there isalready some measurement MORE.
Solution: Minus this error to the reading.
Negative
Before any measurement is made, there isalready some measurement LESS.
Solution: Add this error to the reading
+ More on Micrometer Screw Gauge
Zero Errors
When reading a Micrometer Screw Gauge, errorcan occur due to zero error.
Thus before we use the instrument, we mustcheck for zero error.
Positive
The zero marking on the thimble scale is belowthe datum line.
Negative
The zero marking on the thimble scale is abovethe datum line.
Prefixes
They are used to express physical quantitiesthat are either very large or very small.
Prefixes are based on the SI unit of theparticular physical quantity.
Giga
Symbol: G
10^9
Mega
Symbol: M
10 ^6
Kilo
Symbol: k
10^3
Deci
Symbol: d
10^-1
Centi
Symbol: c
10^-2
Milli
Symbol: m
10^-3
Micro
Symbol: μ
10^-6
Nano
Symbol: n
10^-9
Derived Quantities and their SI Units
They are quantities derived from two or morebase physical quantities
Area
Length × Width
m ²
Volume
Length × Width × Height
m³
Density
Mass ÷ Volume
kg/m³ or kgm-³
Speed
Distance ÷ Time
m÷s or ms-²
Force
Mass × Acceleration
kg m s-²
Base Quantitiesand their SI Units
SI stands for"International Systemof Units"
Length
SI Unit: Metre
Symbol: m
Mass
SI Unit: Kilogram
Symbol: kg
Time
SI Unit: Seconds
Symbol: s
Electrical Current
SI Unit: Ampere
Symbol: A
Temperature
SI Unit: Kelvin
Symbol: K
Amount of Substance
SI Unit: Mole
Symbol: mol
Luminous Intensity
SI Unit: Candela
Symbol: cd
Physical Quantities
They are quantities that can be measured andthey consist of a numerical magnitude/numberand a unit.