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Falling Around the Earth
📖 Falling Around the Earth
Here's a mind-bending fact: the International Space Station is constantly FALLING towards Earth — but it keeps missing! It's moving so fast sideways (28,000 km/h) that by the time it falls, the curved Earth has dropped away beneath it. This is what an orbit really is: falling forever but never hitting the ground. Newton figured this out in the 1600s by imagining a cannon on a very high mountain...
What Keeps Objects in Orbit?
Gravity provides the centripetal force:
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🎯 Exam Focus — Orbits
Examined in Edexcel 1PH0/1 (Paper 1). Context-based questions use real satellite data and mission scenarios. Calculation focus: orbital speeds (v = 2πr / T) and the relationship between orbital radius and period. "Suggest" questions appear for novel orbital scenarios.
What examiners love to ask:
- Explain why gravity provides centripetal force for orbits
- Compare circular and elliptical orbits (speed and force variation)
- Calculate orbital speed from radius and period
- Describe geostationary vs low Earth orbit — uses and differences
- Explain why closer orbits require faster speeds
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What is a protostar?
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This topic in real past papers
Every real exam question we've found on orbits, with a full worked answer.