A moving bicycle has kinetic energy.
If you stop by coasting up a hill until you can't coast any higher,
then the kinetic energy is converted to potential energy. You can
convert it back to kinetic energy by coasting down the other side
of the hill.
If you stop by applying the brakes, then the kinetic energy is
converted to heat in the brakes. Unless you have some really
sophisticated thermodynamic system with you on the bike,
that energy is lost to you, and you can never use it to do
anything with it again.
