Placing a meter rule against a ball oscillating on a spring above a motion detector shows linear damping.
It is left as an exercise to show that for a constant friction force the momentum removed each cycle is the same for each cycle ... hence the linear reduction in peak velocities.
Plotting the Total energy versus time curve for the motion gives the next graph.
Exporting the data to graphical analysis and fitting a power law shows that the total energy of the motion reduces as a quadratic function.
The rate of energy loss in Joules per second is a linear function of time. It is left as an exercise to show why this is so in the special case of simple harmonic motion with a constant friction force.