In this lesson our instructor talks about elastic potential energy. First, he discusses elastic object and a spring example. Then he talks about Hooke's law, elastic potential energy formula, and conservation of energy. Four complete example problems round up this lesson.
If you deform an elastic object (such as a spring or rubber band), it will resist the deformation, attempting to return to its original shape.
The amount of deformation (→x) is measured compared to its original shape. An object with no deformation has →x=0. A 0.1m spring stretched to 0.12m has the same deformation as a 1.0m spring stretched to 1.02m: →x=0.02m.
Different objects will resist deformation at different rates. We show this with the spring constant: k (units in [N/m]).
An elastic object resists deformation with a force of
The negative denotes that the force always points opposite to the deformation (→x).
Deforming an elastic object is a way of storing energy. The amount of potential energy in a spring is
[When working with energy, displacement is no longer measured as a vector. Now it is simply x, the length of the displacement. This is because energy is stored whether we stretch or compress. The direction of deformation doesn't matter: just the magnitude of deformation.]
By the conservation of energy, we can look at the entire energy of the system at the start and end:
Esys, start + W = Esys, end.
[Remember, positive work puts energy into the system, while negative work takes it out.]
Energy: Elastic Potential
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
This book includes a set of features such as Analyzing-Multiple-Concept Problems, Check Your Understanding, Concepts & Calculations, and Concepts at a Glance. This helps the reader to first identify the physics concepts, then associate the appropriate mathematical equations, and finally to work out an algebraic solution.