Because of ash clouding the sky, blocking sunlight for a while.
Energy is the ablity to dow work.
Power is the time rate at which work is done.
independent variable often along x axis, dependent along y axis.
You can set the independent value, from which the dependent follows.
An example would be 2 types of motion. It could be rectilinear or projectile motion. There are various equations for each type. Since you don't want me to tell you the answer, I could just express it in words. Then, it will be up to you to translate into mathematical equations.
For rectilinear motion, the distance traveled is equal to the initial velocity times the time, plus one-half of the acceleration times the square of the time. For projectile motion, the maximum distance is equal to the square of the initial velocity multiplied with the square of the sine of the launch angle, all over twice the gravity.
