What is the ultimate source of energy for an ecosystem?

This is one type of line graph in which the independent variable is time plotted on the x axis and the dependent variable, also numerical, is plotted on the y axis.

In a classical model of the hydrogen atom, the electron moves around the proton in a circular orbit of radius 0.053 nm. what is the electron's orbital frequency? what is the effective current of the electron?

Describe how the motion of a spring being pushed forward and backward is similar to the motion of air particles in a sound wave.