The EarthCambridge IGCSE Physics: Flashcards

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What is the approximate period of Earth's rotation on its axis?

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What is the approximate period of Earth's rotation on its axis?: Approximately 24 hours (one day)
Explain how Earth's tilted axis and rotation cause the apparent daily motion of the Sun.: As Earth rotates on its tilted axis once every 24 hours, different parts of Earth face the Sun at different times. This rotation causes the Sun to appear to move across the sky from east to west during the day, creating the apparent daily motion of the Sun.
How does Earth's rotation explain the cycle of day and night?: As Earth rotates, different parts of the planet face towards and away from the Sun. The side facing the Sun experiences daylight, whilst the side facing away experiences night. This continuous rotation causes the cycle of day and night.
What is the approximate period of Earth's orbit around the Sun?: Approximately 365 days (one year)
Explain why the seasons occur periodically.: Earth's axis is tilted relative to its orbital plane around the Sun. As Earth orbits the Sun over approximately 365 days, the tilt causes different hemispheres to receive different amounts of solar radiation at different times of year, resulting in periodic seasonal variations.
What is the approximate orbital period of the Moon around Earth?: Approximately one month (approximately 27-29 days)
Explain the periodic nature of the Moon's phases.: The Moon orbits Earth approximately once per month. As it orbits, different proportions of its illuminated hemisphere become visible from Earth. This continuous change in the visible illuminated portion creates the periodic cycle of lunar phases.
Define average orbital speed.: Average orbital speed is the distance travelled by an object along its complete orbital path divided by the time taken to complete one orbit. It is the average velocity of an orbiting object over one complete orbital period.
State the equation for calculating average orbital speed.: v = 2πr/T, where v is average orbital speed in m/s, r is the orbital radius in metres, and T is the orbital period in seconds
What do the symbols represent in the equation v = 2πr/T?: v = average orbital speed (m/s); r = orbital radius (m); T = orbital period (s); 2πr = circumference of the circular orbit
Calculate the average orbital speed of Earth around the Sun. (Use r = 1.5 × 10¹¹ m and T = 3.15 × 10⁷ s): v = 2πr/T = (2 × π × 1.5 × 10¹¹) / (3.15 × 10⁷) = (9.42 × 10¹¹) / (3.15 × 10⁷) ≈ 2.99 × 10⁴ m/s or approximately 30 km/s
What causes the apparent daily motion of the Sun across the sky?: Earth's rotation on its axis. As Earth rotates once every 24 hours, an observer on Earth sees the Sun appear to move across the sky from east to west.
Why does the intensity of solar radiation vary with the seasons?: Because Earth's axis is tilted relative to its orbital plane. As Earth orbits the Sun, the tilt means that different hemispheres receive the Sun's rays at different angles throughout the year, causing seasonal variations in radiation intensity.
Describe the relationship between orbital radius and orbital period for objects orbiting a central body.: Objects with larger orbital radii have longer orbital periods. The relationship is given by v = 2πr/T; for objects orbiting the same central body, those further away orbit more slowly and take longer to complete one orbit.
How many times does Earth rotate on its axis whilst orbiting the Sun once?: Approximately 365 times. Since Earth takes approximately 365 days to orbit the Sun and rotates once every 24 hours, it completes approximately 365 rotations per orbit.