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MEASUREMENT

MEASUREMENT. MEASUREMENT. Measurement is the determination of the dimensions,quantity or capacity of an item. To measure physical quantities such as mass,time,length etc we use UNITS. A unit is a fixed quantity used as a standard for measurement. Systems of Units : .

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MEASUREMENT

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  1. MEASUREMENT

  2. MEASUREMENT Measurement is the determination of the dimensions,quantity or capacity of an item. To measure physical quantities such as mass,time,length etc we use UNITS. A unit is a fixed quantity used as a standard for measurement.

  3. Systems of Units : • There are following principle system of units: • C.G.S System : length ? centimeter (cm), mass ? gram (g) time ? second (s). • F.P.S System : length ? foot (ft), mass ? pound (lb), time ? second (s). • M.K.S. System: length ? meter (m), mass ? kilogram (kg), time ? second (s)

  4. SI UNITS…

  5. MASS • Mass of a body is defined as the quantity of matter in the body. • We express mass of an object in gram (g) kilogram (kg) , tonne , quintal etc • The SI unit of mass is kilogram. •  Mass of an object does not change from place to place.

  6. UNITS OF MASS Some of the commonly used units of mass and conversions are : • 1 tonne = 10 quintal • 1 quintal = 100 kg • 1 kg = 1000 g • 1 g = 1000 mg

  7. Measurement of mass

  8. Beam balance • A beam balance consists of a horizontal beam , supported at its centre. • Two pans of equal masses are suspended from both the ends of the beam. • The object is kept on one pan and the standard masses on the other. • When both the pans are equally loaded , the beam is horizontal and the pointer points vertically up at the center.

  9. Physical balance

  10. Physical balance • Physical balances are utilized for precision mass measurement . • A physical balance can measure accurately upto a milligram. • It is provided with a box of standard masses ranging from 1mg to 100g. • It works on the same principle as that of a beam balance.

  11. WEIGHT • Weight is the force exerted on a body by gravity. • This is often expressed in the formula W = mg, where W is the weight, m the mass of the object, and g gravitational acceleration • The SI unit of weight is Newton(N)

  12. Measurement of weightSpring balance

  13. Measurement of weight • A spring balance is used to measure weight of a body • It consists of a spring fixed with a pointer at the upper part anda hook at the lower end to suspend the body • The extension produced in a spring is directly proportional to the gravitational force acting on it.

  14. Comparison between mass and weight

  15. DENSITY • The density of a material is its mass per unit volume. • The symbol most often used for density is ρ (the lower case Greek letter rho). • ρ =m/V • where ρ is the density, m is the mass, and V is the volume. • The SI unit of density is kg/m3

  16. Density of different substances

  17. Question??? Equal masses of iron and common salt have different volumes.

  18. Determining the density of a irregular solid • For an irregular solid like a stone, volume can be found using a graduated measuring cylinder. • The measuring cylinder is half filled with water and the initial water level is noted • Then the stone is immersed in water with the help of a thread and the reading of the water level is noted • The mass of the stone is determined using a physical balance

  19. Thus the density of the stone is found using formula D=M/(Final volume-Initial volume)

  20. RELATIVE DENSITY • Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. • It tells us how dense or heavy is the density of a substance with respect to water • Relative density has no units

  21. Measurement of relative density of a liquid • The relative density of a liquid can be determined with the help of a relative density bottle

  22. Relative density bottle • It is a small, thin walled glass bottle with a stopper having a fine hole. • The mass( m1 ) of the empty bottle is determined using a physical balance. • The liquid whose density is to be measured is filled into the bottle and its mass( m2 ) is determined. • Now clean the bottle thoroughly and find the mass of bottle when it is filled with water(m2 )

  23. Calculating RD • RD=Density of liquid Density of water =Mass of liquid/Volume of liquid Mass of water/Volume of water = (m2 – m1 ) / (m3 – m1 )

  24. Practical application of relative density • Looking at the RD of different substances we can find whether an object or a liquid sinks or floats in water. • If a substance‘s RD is less than one it floats in water. • If a substance‘s RD is more than one it sinks in water.

  25. HYDROMETER • Hydrometer is a device designed to float on a liquid • There are special hydrometers for liquids lighter and denser than water, for testing the purity of milk, for testing the concentration of acids in batteries.

  26. Reference • http://www.convertunits.com/ • http://www.easyunitconverter.com/ (conversion) • http://www.aasd.k12.wi.us/staff/boldtkatherine/MathResources3-6/Math_Measurement.htm#LENGTH (interactive) • http://www.syvum.com/cgi/online/serve.cgi/squizzes/physics/measure1.tdf?0 (quiz)

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