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Our Home: Earth, a Unique Life Sustaining Planet - Size of the Earth

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Earth is not a perfect sphere; its shape is described as an Oblate Spheroid or a Geoid, meaning it is flattened at the poles and bulges at the equator.

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The Equatorial Diameter of the Earth is approximately 12,75612,756 km, while the Polar Diameter is approximately 12,71412,714 km.

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The Equatorial Circumference of the Earth is about 40,07540,075 km, which is slightly larger than the Polar Circumference of 40,00840,008 km.

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The total surface area of the Earth is approximately 510510 million km2km^2. Out of this, about 71%71\% is covered by water (361361 million km2km^2) and 29%29\% by land (149149 million km2km^2).

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The Earth's average density is approximately 5.515.51 g/cm3g/cm^3, making it the densest planet in the Solar System.

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The Earth's mass is estimated to be 5.97×10245.97 \times 10^{24} kg.

📐Formulae

Ddiff=Dequatorial−DpolarD_{diff} = D_{equatorial} - D_{polar}

Average Radius (R)≈6,371 kmAverage\ Radius\ (R) \approx 6,371\ km

Surface Area (A)=4πr2Surface\ Area\ (A) = 4 \pi r^2

Circumference (C)=2πrCircumference\ (C) = 2 \pi r

Volume (V)=43πr3Volume\ (V) = \frac{4}{3} \pi r^3

💡Examples

Problem 1:

Find the difference between the Earth's Equatorial Diameter (12,75612,756 km) and its Polar Diameter (12,71412,714 km).

Solution:

The difference is 4242 km.

Explanation:

We perform vertical subtraction to find the difference between the two diameters: 12756−1271442\begin{array}{r} 12756 \\ -12714 \\ \hline 42 \end{array} This 4242 km difference is the result of the Earth's rotation, which generates centrifugal force that causes the planet to bulge at the center.

Problem 2:

If the total surface area of Earth is 510,000,000510,000,000 km2km^2 and the land area is 149,000,000149,000,000 km2km^2, calculate the area covered by water.

Solution:

The area covered by water is 361,000,000361,000,000 km2km^2.

Explanation:

Subtract the land area from the total surface area: 510000000−149000000361000000\begin{array}{r} 510000000 \\ -149000000 \\ \hline 361000000 \end{array} This confirms that approximately 71%71\% of the Earth's surface is water.

Size of the Earth Class 8 Notes & Examples | CBSE Science