Roller coasters gain potential energy from lift hills to complete their circuits through a transfer of gravitational potential energy to kinetic energy via conservation of energy. Launch coasters use hydraulic or electromagnetic systems to accelerate trains from zero to high speeds without lifts. When designing coasters, circular motion equations involving velocity, radius, and period are considered for safety regarding elements like loops. The first loop-the-loop element was introduced in 1975 due to its smoother g-force profile compared to a hard circular loop. Track design must account for varying loop radii to prevent uncomfortable bumps.