MYP Physics sample question: The life cycle of a Sun-like star

The Sun is a star in the main sequence stage of its life.

1. (a)Put these stages in the correct order for a star like the Sun: white dwarf, nebula, red giant, main sequence, protostar.[3]
   Show the mark scheme for (a)

   • • nebula → protostar → main sequence → red giant → white dwarf (3 marks for all correct; 2 for one error; 1 for two errors)
2. (b)Explain why a main sequence star stays the same size for billions of years.[2]
   Show the mark scheme for (b)

   • • Gravity pulls matter inwards (1)
   • • This is balanced by outward pressure from the energy released by nuclear fusion in the core (1)

Stability questions are about balance. Name both forces or pressures and say that they are equal.