Lesson Worksheet: Fusion in Stars Physics

In this worksheet, we will practice how to describe the process of nuclear fusion in stars and supernovas, and the elements that are produced.


Once the hydrogen in the core of a star runs out, what element does the star begin to fuse next?

  • ALithium
  • BBeryllium
  • CHelium
  • DCarbon
  • EBoron


Nuclear fusion only happens in the of a star, where the and are high enough to allow nuclear fusion to occur.

  • Aouter layers, pressure, viscosity
  • Bouter layers, temperature, pressure
  • Ccore, temperature, pressure
  • Dcore, temperature, viscosity
  • Ecore, temperature, gravitational potential


Once the hydrogen and the helium in the core of a star runs out, what element does the star begin to fuse next?

  • ABeryllium
  • BCarbon
  • CBoron
  • DIron
  • ELithium


Which two of the following elements are not formed in a main sequence star that gives out radiation at a steady rate?

  1. Carbon
  2. Plutonium
  3. Iron
  4. Oxygen
  5. Francium
  • Aa and e
  • Bb and d
  • Cc and e
  • Db and a
  • Eb and e


Which of the following elements can only be formed in a supernova?

  • AHydrogen
  • BHelium
  • CUranium
  • DIron
  • ECarbon


What process is the source of energy in main sequence stars?

  • ANuclear fission
  • BNuclear fusion
  • COxidization


Which element do main sequence stars primarily use for nuclear fusion?

  • AHelium
  • BOxygen
  • CIron
  • DCarbon
  • EHydrogen


Plutonium-239 is an isotope of plutonium with a half-life of approximately 24,000 years. It can be formed in a nuclear reactor, but it is not found naturally. Which of the following reasons explains why this is?

  • AHeavy elements such as plutonium are only formed naturally in supernovas. All of the heavy elements in our solar system were created in a supernova that occurred before the solar system was formed. Since this was more than 4 billion years ago, all of the plutonium that was created in the supernova has decayed.
  • BHeavy elements such as plutonium were only created during the big bang. Since the big bang occurred 13.8 billion years ago, all of the plutonium that was created in it has decayed.
  • CCreating plutonium requires far more energy than any natural process can provide. Plutonium can only be created in nuclear reactors.


What is the most common element in the universe?

  • ACarbon
  • BOxygen
  • CHelium
  • DHydrogen
  • ENeon


The heat generated through nuclear fusion in a star’s core exerts an outward force on the material around it. This would cause the star to expand, but it is balanced by another force acting upon the material in the star, which keeps it stable. What is the other force acting on the matter in the star?

  • AGravity
  • BElectrostatic attraction
  • CElectrostatic repulsion
  • DPressure

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