The inward gravitational forces and outward radiation pressure forces in a stable main-sequence star remain balanced for its entire stable lifetime.
For a specific star with a mass similar to the Sun, this stable lifetime is estimated to be 12 billion years.
This star has currently been in this balanced state for 35% of its total stable lifetime.
Calculate for how many billions of years these forces have been balanced in this star.
42 exam-style questions on Edexcel GCSE Physics 7.3 Stars, covering 7.3.1 Evolution of stars similar to the Sun, 7.3.2 Evolution of massive stars, and 7.3.3 Observing the Universe. Each one has a worked solution and a mark scheme showing where the marks go.