The potential energy of a 40-kg cannonball is 14000 J. How high was the cannon ball to have this much potential energy?

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.