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Earth and Space - The Moon and its phases

Grade 3Cambridge (IGCSE)

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

🔑Concepts

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The Lunar Cycle: The cycle starts with the New Moon (when the Moon is between the Earth and the Sun and appears dark) and progresses to a Full Moon (when the Earth is between the Moon and the Sun). The cycle then reverses back to New Moon. The approximate time for this cycle is T≈28T \approx 28 days.

📐Formulae

1 Lunar Month≈28 days1 \text{ Lunar Month} \approx 28 \text{ days}

Weight on Moon=16×Weight on Earth\text{Weight on Moon} = \frac{1}{6} \times \text{Weight on Earth}

GravityMoon≈1.62 m/s2\text{Gravity}_{Moon} \approx 1.62 \text{ m/s}^2

💡Examples

Problem 1:

If today is a Full Moon, approximately how many weeks will it take to see the next Full Moon?

Solution:

28÷7=4 weeks28 \div 7 = 4 \text{ weeks}

Explanation:

A full lunar cycle takes about 2828 days. Since there are 77 days in a week, we divide 2828 by 77 to find the number of weeks.

Problem 2:

If an astronaut weighs 60 kg60 \text{ kg} on Earth, what would be their approximate weight on the Moon?

Solution:

Weight=606=10 kg\text{Weight} = \frac{60}{6} = 10 \text{ kg}

Explanation:

The Moon's gravity is about 16\frac{1}{6}th of Earth's gravity. Therefore, an object weighs six times less on the Moon than on Earth.

Problem 3:

Calculate the number of days it takes for the Moon to go from a New Moon to a Full Moon (halfway through the cycle).

Solution:

282=14 days\frac{28}{2} = 14 \text{ days}

Explanation:

A full cycle from New Moon back to New Moon is 2828 days. A Full Moon occurs halfway through the cycle, which is 1414 days.