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Our Home: Earth, a Unique Life Sustaining Planet - What Do the Planets of Our Solar System Look Like?

Grade 8CBSE

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

🔑Concepts

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The Solar System consists of the Sun and eight planets. Earth is unique because it is the only known planet that supports life due to the presence of liquid water (H2OH_2O), an atmosphere with 21%21\% Oxygen (O2O_2), and a moderate temperature range.

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Earth lies in the 'Goldilocks Zone' or Circumstellar Habitable Zone, where the distance from the Sun allows temperatures to remain between the freezing and boiling points of water.

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The Inner Planets (Mercury, Venus, Earth, Mars) are terrestrial/rocky planets with high densities and solid surfaces.

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The Outer Planets (Jupiter, Saturn, Uranus, Neptune) are Gas Giants or Ice Giants, primarily composed of Hydrogen (H2H_2), Helium (HeHe), and ices like Methane (CH4CH_4).

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Venus is the hottest planet in the solar system due to a runaway greenhouse effect caused by an atmosphere that is 96%96\% Carbon Dioxide (CO2CO_2).

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Mars is known as the 'Red Planet' because of the presence of Iron(III) oxide (Fe2O3Fe_2O_3) on its surface.

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The distance between planets and the Sun is often measured in Astronomical Units (AU), where 1 AU1 \text{ AU} is the average distance from the Earth to the Sun.

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Gravity on a planet's surface depends on its mass (MM) and radius (RR), governed by the formula for acceleration due to gravity gg.

📐Formulae

1 AU≈1.496×108 km1 \text{ AU} \approx 1.496 \times 10^8 \text{ km}

g=GMR2g = \frac{GM}{R^2}

W=m×gW = m \times g

Density(ρ)=Mass(M)Volume(V)\text{Density} (\rho) = \frac{\text{Mass} (M)}{\text{Volume} (V)}

💡Examples

Problem 1:

If the acceleration due to gravity on Earth is ge=9.8 m/s2g_e = 9.8 \text{ m/s}^2 and on Mars it is gm=3.7 m/s2g_m = 3.7 \text{ m/s}^2, calculate the weight of an astronaut with a mass of 70 kg70 \text{ kg} on both planets.

Solution:

On Earth: We=70×9.8=686 NW_e = 70 \times 9.8 = 686 \text{ N}. On Mars: Wm=70×3.7=259 NW_m = 70 \times 3.7 = 259 \text{ N}.

Explanation:

Weight is the product of mass and the local acceleration due to gravity (W=mgW = mg). While mass remains constant at 70 kg70 \text{ kg}, the weight changes because gg is different on Mars.

Problem 2:

Calculate the difference in the equatorial diameters of Earth (12,756 km12,756 \text{ km}) and Mars (6,792 km6,792 \text{ km}) using vertical subtraction.

Solution:

12756−67925964\begin{array}{r} 12756 \\ - 6792 \\ \hline 5964 \end{array}

Explanation:

The difference in diameter between Earth and Mars is 5,964 km5,964 \text{ km}, showing that Earth is nearly twice as large as Mars.

Problem 3:

Jupiter is approximately 5.2 AU5.2 \text{ AU} away from the Sun. Express this distance in kilometers.

Solution:

5.2 AU×(1.496×108 km/AU)=7.7792×108 km5.2 \text{ AU} \times (1.496 \times 10^8 \text{ km/AU}) = 7.7792 \times 10^8 \text{ km}

Explanation:

By multiplying the distance in Astronomical Units by the value of 1 AU1 \text{ AU} in kilometers, we find that Jupiter is approximately 777.92777.92 million kilometers away from the Sun.