posted Jan 30, 2015, 12:02 AM by ranmini@charliesresearch.com
[
updated Sep 12, 2017, 9:48 PM by Upali Salpadoru
]
What do we measure?
Do you know that all our measure ments are based on 7 basic measurements?
What are they?
Symbols used here The 'fundamental' units (Basic units) are named in red. Others are 'Derived units'. Measurement | Symbol | Units |
| Vector / Scalar. | Area. | A | m2 | Square meters. | Scalar | Acceleration. | a | ms-2 | Meters per second per second. | Centre of gravity Centre of mass. | G | An imaginary point through which the weight of a body may be considered to act. | | Luminosity | Cd. | candela | | Scalar | Current. | I or i. | A = Amperes. | Scalar | Density. | r or d. | g.cm-3 | Scalar | Displacement. | d. | M =Meter. | Vectar | Energy. | E | J=Joule. | Scalar | Force. | F or f. | N = Newton. | Vector. | Force gravitational. | g. |
|
| Vector. | Height. | h. | m. |
| Scalor. | Mass. | m. | kg= Kilogram. | Scalar | | Mole | mol | A | = 6.02 x1023 | Scalar | Power. | P | W = Watt. | Scalar | Pressure. | Pr. | Pa.= Pacal. Pa = Nm-2 | Scalar | Period. (Time) | t. | s= second. | Scalar | Speed. | ms-1 |
|
| Scalar | Temperature . | T. | K | Kelvin | Scalar | Velocity. | V | ms-1 |
| Vectar. | Work. | Wk. | J= Joule. |
| Scalar. |
This is not according to the alphabetical order.
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Word
formula
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Analysis
|
In
symbols..
|
|
Area = L
x L
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Area
= m x m.
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A= m2
|
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Volume =
L xL xL
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Volume =
mxmxm.
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V = m3
|
|
Density.=mass/
volume.
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Density
= m/v.
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d= .kg.m-3
|
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Velocity
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Velocity=
meters/ seconds
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V = ms-1.
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Acceleration.
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Acc.= Vfinal -Vinitial / time
=
Change in Velocity/ time.
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a= ms-2
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Energy
(Gr. potential)
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Eg= mass
x gravity x height.
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J = mgh.
|
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Energy
(Work)
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Ew =
Force x distance.
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J= Nm.
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Energy
(Electrical)
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Ee =
Volt x current x time.
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J = Vit.
J =i2rt.
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Energy
(Heat)
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Heat
=Mass x specific heat x time.
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H = mct.
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Energy
(Kinetic)
|
Ek = ½
mass x velocity 2
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Ek =
1/2kg.v2.
|
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Power
|
Energy
changed / time.
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P = J/t
. | | Force | mass x acceleration | F= ma. | A few more practical units.
|
Name
|
symbol
|
Definition
|
|
Frequency
|
Hz
|
Number of occurrence in one second.
|
|
Kilo watt hour.
|
kWH.
|
Quantity of electrical energy consumed in one hour.
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|
Horse power.
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Hp.
|
750 W. ( Average power of a
horse)
|
|
Micro farad.
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μF
|
Electrical charge in a capacitor.
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Decibel.
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dB
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Intensity of a sound.
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Richter .
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Log. Unit for Earth quakes.
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For Richter scale, Mohr's hardness and wind scale click: Physical tables.
Prefixes used to change the size of units.
Some problems in using
formulas.
1.0
The volume of a solid block is 20
m3 . The density is 6 kg m3.
What is the weight of the mass?
2.0
John getting a standing start runs 100m. in 15 s. gradually increasing velocity . Find
the final velocity?
3.0 Jane has a mass of 50 kg and her cycle 20 kg. On riding at a speed of 10ms-1 a snake decides to cross
her path. She brings the bike to a stop in 2 seconds. What was her braking
power.
4.0
1.0 kW. Steel kettle of 250g. is used to heat 2
litres of water at 20C . Find the minimum time it will take to boil the water.
5.0.
A car and passengers having a mass of 1500 kg. speeds
up from 15m-s 30 m-s in 3 seconds. Find the force car has used.
For solutions click- Answer page =
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