General ScienceMadrid 2026Question 2A
X-linked inheritance
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Problem statement
Question 2.A.- A communications satellite of mass 1500 kg has been placed in a circular orbit around the Earth. The mechanical energy of the satellite in its orbit is $-4.51\cdot10^{10}$ J.
a) (1 mark) Calculate the radius of the orbit and the speed of the satellite in it.
b) (0.8 marks) How many revolutions around the Earth does the satellite make in one day?
c) (0.7 marks) Determine the escape speed of the satellite from its orbit.
Data: Universal Gravitation Constant, $G = 6.67\cdot10^{-11}\ \text{N m}^2\,\text{kg}^{-2}$; Mass of the Earth, $M_T = 5.97\cdot10^{24}$ kg.
Source: Madrid university entrance exam (PAU, Spain) · 2025-2026 · Ordinary session · Physics · Question 2.A. Official exam set by the public universities of the Community of Madrid, to whom it belongs; translated from Spanish and reproduced with its source in order to explain it for teaching purposes.What this lesson answers
- What does the statement tell us before we calculate anything?
- Why doesn't the satellite fall?
- Where does the energy of a circular orbit come from?
- a) Why does the energy fix the radius?
- a) Why does the speed come out without using the radius?
- b) How many revolutions fit in a day?
- c) What speed would be needed never to come back?
- The three answers and how to check them
- Common mistakes to avoid
- Exam tips
- If you want full marks
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