Wile E. Coyote's plan to use the ACME Super Spring to launch himself towards the Road Runner is based on the principles of potential and kinetic energy. Initially, when Wile E. compresses or stretches the spring, he stores potential energy in it. This energy is then converted into kinetic energy—the energy of motion—when he releases the spring, allowing it to propel him forward.
However, Wile E. made a critical oversight in understanding how springs work. While the spring does convert potential energy into kinetic energy as it launches him, once it reaches its maximum stretch, the spring then needs to return to its original shape. In doing this, it once again stores potential energy.
At this point, the potential energy that has been stored during the stretching phase is converted back into kinetic energy as the spring snaps back. This action is not directed toward propelling Wile E. forward but instead generates an equal and opposite force that ultimately pulls him back towards the fixed point of the spring. Consequently, rather than soaring gracefully after the Road Runner, Wile E. is yanked back by the spring's elastic pull, leading to an unfortunate collision with the rock.
In summary, Wile E.’s spring plan failed because he didn’t account for the fact that the energy stored in the spring can act in multiple ways: first launching him forward, and then, once the spring’s extension is maximized, pulling him back as it snaps to its original position, resulting in a painful outcome. Thus, his understanding of the energy transformations in the spring did not lead to the desired result.