E.5.1—Stellar equilibrium Topic Practice
E.5.1—Stellar equilibrium Topic Practice

IB Physics syllabusPhysics SL/HLFirst assessment 2025
Practise explaining stellar equilibrium by linking fusion in a main-sequence star to outward pressure that balances inward gravitational pressure.
How this is tested
- state the force balance in a main-sequence star as outward radiation or thermal pressure against inward gravity
- explain how photons from fusion contribute to outward pressure, helping the Sun keep a stable radius
- use a collapse condition such as the Jeans criterion to judge whether a nebula will form a stable star
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