If the energy was converted perfectly from poten-
tial energy to kinetic energy, Newton's cradle
would continue to run forever, unless acted on by
another outside force.
However, that is not the case. Some of that energy
is getting converted into a form that does not work
toward keeping the cradle in motion. Predict what
the energy conversions might be that do not keep
the cradle in motion.
Answer in complete sentences.