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प्रश्न
How close was your earlier guess? Discuss.
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उत्तर
Our guess for the stamp was 27, but the actual answer is 28. So, we can say that our guess was quite close to the correct answer.
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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?
What are the S.I. units of
- mass
- length
- time and
- temperature.
Write their names and symbols.
Solve the numerical example.
When the planet Jupiter is at a distance of 824.7 million kilometers from the Earth, its angular diameter is measured to be 35.72'' of arc. Calculate the diameter of Jupiter.
Fill in the following chart.
| Property | Definition | Basic Unit | Instrument used for measuring |
| Length | |||
| Mass | |||
| Volume | |||
| Time |
Difference in size 
Do this for yourself and find the difference.
Measure the yellow rectangle. It is ________ cm long.
How many stamps can be placed along its length?
How many stamps are needed to cover the rectangle?
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.
- A longer boundary around the lake will help more birds to lay their eggs. So which lake should be kept for birds? Which lake should be used for boats?
What is the unit of measurements of very small lengths?
What is the unit of measurements of very small lengths?
SI unit of electric current is ______.
The SI unit of mass is kg.
Consider a sunlike star at a distance of 2 parsecs. When it is seen through a telescope with 100 magnification, what should be the angular size of the star? Sun appears to be (1/2)° from the earth. Due to atmospheric fluctuations, eye can’t resolve objects smaller than 1 arc minute.
According to the modern definition, what fraction of a second does light travel to define one metre?
What is the SI unit of length?
Why is the speed of light used to define the metre?
