Eighth Grade · Science · week 11

Potential energy stores

Identify gravitational, elastic, and chemical potential energy in real objects, and compute gravitational PE using PE = m x g x h.

Potential energy is stored energy from position or condition. Gravitational PE is stored in anything raised against gravity: PE = m x g x h, with g about 9.8 m/s^2 near Earth's surface -- we will round g to 10 m/s^2 this week for easy arithmetic.

Elastic potential energy is stored in anything stretched or squeezed and ready to spring back, like a drawn bow or a compressed spring. Chemical potential energy is stored in bonds between atoms, released when they break and reform, like the energy in food or a battery.

📋 For the teacher
Teach it (10–15 min):
  • Point out real examples of all three types around the house in one short walk.
  • Practice the PE formula with g rounded to 10, mentioning 9.8 is the more exact value used later.
  • Ask "where did this stored energy come from?" -- potential energy usually has to be put in by something else first.
Talk about it:
  • What do gravitational, elastic, and chemical potential energy have in common?
  • Why does lifting an object higher increase its potential energy?

Mastery looks like: They compute gravitational PE correctly from mass and height, and classify a real example as gravitational, elastic, or chemical.

Common stumbles: Forgetting to include height or mass in the calculation; confusing potential energy (stored) with kinetic energy (already moving).

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