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Earth and Space - Earth's Rotation and Revolution

Grade 5IB

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

🔑Concepts

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Earth's Rotation: The Earth spins on its imaginary axis from West to East. One full rotation takes approximately 2424 hours, which creates the cycle of day and night.

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The Axis and Tilt: The Earth's axis is not straight; it is tilted at an angle of 23.5∘23.5^\circ. This tilt is responsible for the varying lengths of day and night and the changing seasons.

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Earth's Revolution: While rotating, the Earth also travels around the Sun in a fixed path called an orbit. This movement is called revolution and takes approximately 365.25365.25 days to complete one cycle.

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The Leap Year: Because a revolution takes 365365 days and 66 hours (0.250.25 of a day), these extra hours are added up every four years (0.25×4=10.25 \times 4 = 1 day) to create a Leap Year consisting of 366366 days.

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Seasons: Seasons are caused by the 23.5∘23.5^\circ tilt of the Earth's axis and its revolution around the Sun. When a hemisphere is tilted towards the Sun, it experiences Summer; when tilted away, it experiences Winter.

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Apparent Motion: The Sun appears to rise in the East and set in the West because of the Earth's counter-clockwise rotation (15∘15^\circ per hour).

📐Formulae

1 Rotation≈24 hours1 \text{ Rotation} \approx 24 \text{ hours}

1 Revolution≈365.25 days1 \text{ Revolution} \approx 365.25 \text{ days}

Axial Tilt=23.5∘\text{Axial Tilt} = 23.5^\circ

Leap Year=(365×4)+1=1461 days per 4-year cycle\text{Leap Year} = (365 \times 4) + 1 = 1461 \text{ days per 4-year cycle}

💡Examples

Problem 1:

If the Earth takes 365.25365.25 days to complete one revolution, how many extra days are accumulated over a period of 1212 years?

Solution:

12×0.25=3 days12 \times 0.25 = 3 \text{ days}

Explanation:

Every year, there is an extra 0.250.25 day (6 hours) beyond the standard 365365 days. By multiplying the number of years by 0.250.25, we find that 33 full days are added to the calendar (resulting in 33 leap years) over a 1212-year period.

Problem 2:

Explain why a person standing on the Equator moves faster than someone standing near the North Pole due to rotation.

Solution:

Speed=DistanceTime\text{Speed} = \frac{\text{Distance}}{\text{Time}}

Explanation:

The Earth is widest at the Equator. Since the entire Earth completes one rotation in 2424 hours, a point on the Equator must travel a much larger distance (40,07540,075 km) in the same amount of time compared to a point near the pole, resulting in a higher rotational speed.

Problem 3:

During the month of June, the Northern Hemisphere is tilted towards the Sun. What season is the Southern Hemisphere experiencing?

Solution:

Winter

Explanation:

Because of the Earth's 23.5∘23.5^\circ tilt, when the Northern Hemisphere is tilted towards the Sun (receiving direct sunlight), the Southern Hemisphere is tilted away from the Sun (receiving indirect sunlight), leading to opposite seasons.