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प्रश्न
Now guess the length and width of many other things. Measure and find the difference between your measure and your guess.
| Size of | Your guess in cm | Your measure in cm | ||
| Length | Width | Length | Width | |
| 100 Rupee note | ||||
| 10 Rupee note | ||||
| 20 Rupee note | ||||
| 5 Rupee note | ||||
| Post card | ||||
| Math-Magic book | ||||
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उत्तर
| Size of | Your guess in cm | Your measure in cm | ||
| Length | Width | Length | Width | |
| 100 Rupee note | 16.2 | 7.0 | 15.5 | 7.3 |
| 10 Rupee note | 13.0 | 6.0 | 13.7 | 6.3 |
| 20 Rupee note | 15.0 | 6.5 | 14.8 | 6.3 |
| 5 Rupee note | 11.5 | 6.5 | 11.7 | 6.3 |
| Post card | 14.0 | 9.0 | 14.5 | 9.5 |
| Math-Magic book | 28.0 | 22.0 | 28.5 | 21.5 |
Difference between my guess and measurement
| Size of | Difference in cm | |
| Length | Width | |
| 100 Rupee note | 0.5 cm | 0.3 cm |
| 10 Rupee note | 0.7 cm | 0.3 cm |
| 20 Rupee note | 0.2 cm | 0.2 cm |
| 5 Rupee note | 0.5 cm | 0.2 cm |
| Post card | 0.5 cm | 0.5 cm |
| Math-Magic book | 0.5 cm | 0.5 cm |
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संबंधित प्रश्न
The principle of ‘parallax’ in section 2.3.1 is used in the determination of distances of very distant stars. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth’s orbit ≈ 3 × 1011m. However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1” (second) of arc or so. A parsec is a convenient unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1” (second) of arc from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of meters?
Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity):
the number of strands of hair on your head
Fill in the blank.
In the ............ system, length is measured in centimetres.
Exercise
Rulers, measuring tapes and metre scales are used to measure ______
Can you find the diameter of a thin wire of length 2 m using the ruler from your instrument box?
Which line is longer? C or D? Measure each line. How good is your guess?
Guess whose tail is the longest. Now measure the tails. How good is your guess?
What is Dinesh’s height in metres? _____ m _____ cm.
Measure the yellow rectangle. It is ________ cm long.
Arbaz plans to tile his kitchen floor with green square tiles. Each side of the tile is 10 cm. His kitchen is 220 cm in length and 180 cm wide. How many tiles will he need?
Can you think of how to cut a postcard so that you can pass through it?
There are two beautiful lakes near a village. People come for boating and picnics in both the lakes. The village Panchayat is worried that with the noise of the boats the birds will stop coming. The Panchayat wants motorboats in only one lake. The other lake will be saved for the birds to make their nests.
- How many cm is the length of the boundary of lake A in the drawing?(use thread to find out)
In which SI unit, you can measure your height?
What is the unit of length?
Larger unit for measuring time is ______.
The radius of atom is of the order of 1 Å and the radius of nucleus is of the order of fermi. How many magnitudes higher is the volume of atom as compared to the volume of nucleus?
- The earth-moon distance is about 60 earth radius. What will be the diameter of the earth (approximately in degrees) as seen from the moon?
- Moon is seen to be of (½)°diameter from the earth. What must be the relative size compared to the earth?
- From parallax measurement, the sun is found to be at a distance of about 400 times the earth-moon distance. Estimate the ratio of sun-earth diameters.
In an experiment to estimate the size of a molecule of oleic acid 1 mL of oleic acid is dissolved in 19 mL of alcohol. Then 1 mL of this solution is diluted to 20 mL by adding alcohol. Now 1 drop of this diluted solution is placed on water in a shallow trough. The solution spreads over the surface of water forming one molecule thick layer. Now, lycopodium powder is sprinkled evenly over the film and its diameter is measured. Knowing the volume of the drop and area of the film we can calculate the thickness of the film which will give us the size of oleic acid molecule.
Read the passage carefully and answer the following questions:
- Why do we dissolve oleic acid in alcohol?
- What is the role of lycopodium powder?
- What would be the volume of oleic acid in each mL of solution prepared?
- How will you calculate the volume of n drops of this solution of oleic acid?
- What will be the volume of oleic acid in one drop of this solution?
What is an Astronomical Unit (AU)?
