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Our Universe - The Moon and its phases

Grade 3ICSE

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

🔑Concepts

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The Moon is the Earth's only natural satellite, orbiting at an average distance of approximately 384,400 km384,400 \text{ km}.

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The Moon is a non-luminous object; it does not produce its own light but reflects light from the Sun toward the Earth.

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The surface of the Moon is rocky and dusty, containing large bowl-shaped depressions called craters.

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The Moon does not have an atmosphere (air) or water, which is why life cannot exist there.

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The gravity on the Moon is much weaker than Earth's gravity, specifically it is 16th\frac{1}{6}^{th} of the Earth's gravitational pull.

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The Moon takes approximately 27.327.3 days to complete one revolution around the Earth.

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The 'Phases of the Moon' are the different shapes of the lit portion of the Moon as seen from Earth. These change as the Moon moves in its orbit.

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Main phases include: New Moon (invisible), Crescent Moon, Half Moon (First/Last Quarter), Gibbous Moon, and Full Moon.

📐Formulae

WeightMoon=WeightEarth6Weight_{Moon} = \frac{Weight_{Earth}}{6}

1 Lunar Cycle (New Moon to New Moon)≈29.5 days1 \text{ Lunar Cycle (New Moon to New Moon)} \approx 29.5 \text{ days}

1 Revolution≈27.3 days1 \text{ Revolution} \approx 27.3 \text{ days}

💡Examples

Problem 1:

If a small robot weighs 18 kg18 \text{ kg} on Earth, how much will it weigh on the surface of the Moon?

Solution:

18 kg÷6=3 kg18 \text{ kg} \div 6 = 3 \text{ kg}

Explanation:

Since the Moon's gravity is 16\frac{1}{6} of the Earth's gravity, we divide the weight on Earth by 66 to find the weight on the Moon.

Problem 2:

Identify the phase of the Moon when we can see the entire circular bright side from Earth.

Solution:

Full Moon

Explanation:

A Full Moon occurs when the Earth is between the Sun and the Moon, allowing us to see the entire side of the Moon that is lit by the Sun.

Problem 3:

Why do we see different shapes of the Moon throughout the month?

Solution:

Due to the Moon's revolution around the Earth.

Explanation:

As the Moon orbits the Earth, different parts of its sunlit surface are visible to us. These changing visible portions are called the phases of the Moon.