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Estimating weight of good

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Rural Technology

Due to convention, many times we use different units than SI units. Many times things are sold using different measurement. For example Iron is sold on per Kg weight. This means though we measure dimension for manufacturing ‘Table’ in length, still we need to measure its weight. For making estimate of a job, we have to calculate the weight of the angle used. The formula for calculation is given below:

Weight of material = Density of material × volume of job. Volume of a job = Area of cross section of an object × length of object Density of iron is 7.87 gm/cm3 or 7870 Kg/m3

Example:

1) Calculate a weight of 4 cm diameter iron rod of 100 cm. in length. Diameter = 10 cm Area = p / 4 × D2 Area = 3.14 / 4 × (4 × 4) = 12.56 cm2 Volume = Area × Length = 12.56 × 100 = 1256 cm3 Weight = Density × Volume = 7.87 × 1256 = 9884.72 gm = 9.88 Kg 2) Calculate weight of a 25 × 25 × 3 mm angle of length 3 meter Length = 25 mm = 2.5cm, thickness = 3 mm = 0.3 cm, Length = 3 mtr = 300cm.

Area of cross section = (Area of vertical cross section) + Area of horizontal cross section

= (Length × breadth) + (Length × breadth) = (2.5 × 0.3) + (2.5 × 0.3) = 1.5 cm2 Length = 3 mtr. = 300 cm Volume= Area × Length = 1.5 × 300 = 450 cm3 Weight = Density × Volume = 7.87 × 450 = 3541.5 gm = 3.54 Kg

What you have learnt

In this chapter, we have learned about measurement, types of measurement, base unit and derived units. We have studies quantitative and qualitative measurement. We also discussed SI units and International standards of units. We also discussed about factors affecting selection of instruments, least count of instrument. At the end, we learned to calculate weight of goods.

Terminal Questions

1) Write down factors affecting selection of measuring instruments. 2) Estimate weight of iron flat of following dimension. L = 3 meter, Breadth = 0.5 meter, thickness = 5 cm Density of iron is 7.87 gm/cm3 or 7870 Kg/m3

Answer to Intext Questions

1.1 1) We got good yield of crop. Qualitative 2) We got 5 quintals of rice. Quantitative 3) This year there is enough rain. Qualitative 4) This year we got 500mm rain. Quantitative 5) This construction needs lot of cement. Qualitative 6) This construction needs 5 bags of cement. Quantitative 1.2 i) 0.5m, 5500m, 1.6km, 1.02m

ii) 1 Kg 1.3 i) vernier caliper, Ampere meter, Thermometer, Balance ii) 0.01cm, 1mm, 1 second

Suggested activities

1) Measure dimensions of your house. 2) Read and write down different parameters and units written on biscuit or any other packet.

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Rural Technology