The goal of this activity is for students to grapple with the idea of energy without it being named. Students investigate energy stored in a spring that does work on a cart. They determine a mathematical model used to predict how to achieve a particular cart speed based on the distance the spring is stretched.

During the subsequent investigation, students collect data and construct a model that allows them to predict how different springs can achieve the same effect (cause the cart to move at a specified speed). Students can collect data using a variety of tools, including motion detectors, photogates, the Go Direct Sensor Cart, or Motion Encoders.

This investigation should result in graphs of spring constants. Students will use their graphs as a tool to investigate how one might determine the correct length of stretch that will match a particular speed.

Students should finish the activity with the knowledge that the area under the force vs. displacement curve provides a method for predicting the resulting velocity of the cart for any given spring.


  • Design and perform an investigation.
  • Draw a conclusion from evidence.
  • Understand that the area under the curve of force vs. displacement represents a physically meaningful quantity that involves speed of an object.