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प्रश्न
A particular star is at a distance of about 8.1 × 1013 km from the Earth. Assuring that light travels at 3 × 108 m per second, find how long does light takes from that star to reach the Earth.
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उत्तर
The distance between Star and Earth = 8.1 × 1013 km = 8.1 × 1013 × 103 m
Since, light travels at 3 × 108 m per second.
So, time taken by light to reach the Earth = `(8.1 xx 10^13 xx 10^3)/(3 xx 10^8)`
= `(8.1 xx 10^16)/(3 xx 10^8)`
= `8.1/3 xx 10^8`
= 2.7 × 108 s
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संबंधित प्रश्न
Mass of earth is 5.97 × 1024 kg and the mass of the moon is 7.35 × 1022 kg. What is the total mass?
The table shows the mass of the planets, the sun and the moon in our solar system.
| Celestial Body |
Mass (kg) | Mass (kg) Standard Notation |
| Sun | 1,990,000,000,000,000,000,000,000,000,000 | 1.99 × 1030 |
| Mercury | 330,000,000,000,000,000,000,000 | |
| Venus | 4,870,000,000,000,000,000,000,000 | |
| Earth | 5,970,000,000,000,000,000,000,000 | |
| Mars | 642,000,000,000,000,000,000,000,000,000 | |
| Jupiter | 1,900,000,000,000,000,000,000,000,000 | |
| Saturn | 568,000,000,000,000,000,000,000,000 | |
| Uranus | 86,800,000,000,000,000,000,000,000 | |
| Neptune | 102,000,000,000,000,000,000,000,000 | |
| Pluto | 12,700,000,000,000,000,000,000 | |
| Moon | 73,500,000,000,000,000,000,000 |
- Write the mass of each planet and the Moon in scientific notation.
- Order the planets and the moon by mass, from least to greatest.
- Which planet has about the same mass as earth?
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| Planet | Distance from Sun (km) |
Distance from Sun (km) Standard Notation |
| Earth | 149,600,000 | 1.496 × 108 |
| Jupiter | 778,300,000 | |
| Mars | 227,900,000 | |
| Mercury | 57,900,000 | |
| Neptune | 4,497,000,000 | |
| Pluto | 5,900,000,000 | |
| Saturn | 1,427,000,000 | |
| Uranus | 2,870,000,000 | |
| Venus | 108,200,000 |
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- Order the planets from closest to the sun to farthest from the sun.
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| Titanium | 7.95 × 10–26 |
| Lead | 3.44 × 10–25 |
| Silver | 1.79 × 10–25 |
| Lithium | 1.15 × 10–26 |
| Hydrogen | 1.674 × 10–27 |
- Which is the heaviest element?
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- List all five elements in order from lightest to heaviest.
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