Reference level — Science definition
The chosen height where gravitational potential energy is defined as zero; only changes in PE have physical meaning.
Where it is taught
- Kinetic & Potential Energy — Work, Energy & Momentum, Physics & Environmental Science, Grade 12
In use
8 m/s² near Earth's surface, and h is height above some chosen reference level.
Kinetic & Potential Energy
Questions using reference level
Problem 1
Explain why gravitational potential energy depends on the reference level you choose, and why that is not a problem in practice.
Answer and explanation
Because PE = mgh measures height h from a chosen zero level, the numerical value of PE changes if you pick a different reference. This is not a problem because only changes in PE (as an object rises or falls) affect motion, and those changes come out the same no matter where you place the reference level.