Energy Loss in a Lightly Damped Mass/Spring System

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A lightly damped mass/spring system oscillates back and forth. The 20-kg block is attached to a spring of constant 10 N/m and rides on a frictionless floor. The distance grid is in meters and the times are shown in seconds. Study the graphs of the block's kinetic energy, the spring's potential energy, and the system's total energy as functions of time. Why does the energy decrease?


  1. At any point in the block's motion, "measure" the kinetic and potential energies from the graphs. Can you verify that they are calculated correctly? (Use the Physlet Assistance to display the block's instantaneous velocity.)
  2. What happens to the energy as time goes on? Why?


See Serway and Beichner, Physics For Scientists and Engineers 5th Edition, Section 13.6

Illustration written by Steve Mellema and Chuck Niederriter