A student uses this model of a star leaving the main sequence:
core hydrogen becomes depleted → \rightarrow\,→ core contracts → \rightarrow\,→ outer layers expand.
Which statement explains why contraction of the core and expansion of the outer layers can both occur?
Gravity disappears in the core but continues in the outer layers.
Thermal expansion disappears in the outer layers but continues in the core.
Gravity must become stronger than outward pressure throughout the star.
The balance of gravity and outward pressure differs between the regions.
75 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.