Potential Energy (College Board AP® Physics 1: Algebra-Based)

Potential energy

• A system has potential energy if both:

  • the system is composed of two or more objects

  • the objects interact with each other only through conservative forces

• Potential energy is:

  • independent of motion

  • associated with the positions of objects within a system

  • a scalar quantity with magnitude only

• Examples of potential energy, , include:

  • gravitational potential energy

  • elastic potential energy

• A change in the potential energy of a system is a measure of work done on the system or by the system

• The work done by a conservative force exerted on a system is path-independent

• Therefore, the potential energy of a system is also path-independent

• An object that is lifted through a height and placed on a shelf has potential energy

  • The gravitational force would act on the object if the shelf was removed

  • This would result in the potential energy being transformed into motion (translational kinetic energy) as the object falls

• The object would gain the same amount of potential energy no matter what path was taken as long as it was lifted through an equal height

• The point of zero potential energy is not absolute; it can be changed

  • Zero potential energy for a given system can be defined by the observer

  • This can help to simplify or assist the analysis of the system

• For example, consider the plant on the bookcase:

  • The point of zero potential energy could be defined as:

    • the center of Earth

    • ground level on the street outside

    • the floor of the room

    • the shelf below

  • The observer can choose the most appropriate zero point

  • This is generally the starting position of the object

  • This allows for the change in potential energy to be calculated