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The Universe - The Sun and Planets

Grade 4ICSE

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

🔑Concepts

The Solar System consists of the Sun at the center and 88 planets that revolve around it in fixed paths called orbits.

The Sun is a massive ball of burning gases, primarily HydrogenHydrogen and HeliumHelium, with a surface temperature of approximately 6000C6000^{\circ}C.

Planets do not have their own light; they reflect the light of the Sun. They are classified into Inner Planets (Mercury, Venus, Earth, Mars) and Outer Planets (Jupiter, Saturn, Uranus, Neptune).

Rotation is the spinning movement of a planet on its own axis. Earth's rotation takes 2424 hours and causes Day and Night.

Revolution is the movement of a planet around the Sun. Earth takes 36514365\frac{1}{4} days to complete one revolution, which causes seasons.

Mercury is the closest planet to the Sun, while Neptune is the farthest. Venus is the hottest planet due to a thick atmosphere of CO2CO_2 (Carbon Dioxide) that traps heat.

Earth is known as the 'Blue Planet' because about 71%71\% of its surface is covered with H2OH_2O (water).

Jupiter is the largest planet, so big that about 13001300 Earths could fit inside it.

📐Formulae

1 Solar Day=24 hours1 \text{ Solar Day} = 24 \text{ hours}

1 Year (Earth)=36514 days1 \text{ Year (Earth)} = 365 \frac{1}{4} \text{ days}

Leap Year=365 days+(14×4) day=366 days\text{Leap Year} = 365 \text{ days} + (\frac{1}{4} \times 4) \text{ day} = 366 \text{ days}

Order of Planets:MeVEMaJSUN\text{Order of Planets}: \text{Me} \rightarrow \text{V} \rightarrow \text{E} \rightarrow \text{Ma} \rightarrow \text{J} \rightarrow \text{S} \rightarrow \text{U} \rightarrow \text{N}

💡Examples

Problem 1:

If a planet takes 8888 Earth days to complete one revolution, is it closer to or further from the Sun compared to Earth?

Solution:

It is closer to the Sun.

Explanation:

According to planetary motion, planets closer to the Sun have smaller orbits and move faster. Since 88<3651488 < 365\frac{1}{4}, the planet (Mercury) is closer to the Sun than Earth.

Problem 2:

Why does the Sun appear much larger and brighter than other stars seen at night?

Solution:

Because of its relative distance to Earth.

Explanation:

The Sun is the nearest star to Earth, at a distance of approximately 1.5×108 km1.5 \times 10^8 \text{ km}. Other stars are many light-years away, making them appear as tiny dots.

Problem 3:

Calculate the number of hours in a Leap Year.

Solution:

8784 hours8784 \text{ hours}

Explanation:

A Leap Year has 366366 days. Since 1 day=24 hours1 \text{ day} = 24 \text{ hours}, total hours = 366×24=8784 hours366 \times 24 = 8784 \text{ hours}.