Final answer:
The cocking phase of a throw ends with the initiation of shoulder rotation, leading into the rapid acceleration of the throw. The PE-KE transformation for a javelin involves potential energy converting to kinetic energy from release to when it strikes the ground.
Step-by-step explanation:
The end of the cocking phase in the throwing motion is signaled by d) Initiation of shoulder rotation. This phase is crucial for preparing the arm for the rapid acceleration that will occur in subsequent phases.
Regarding the PE-KE (Potential Energy-Kinetic Energy) transformations for a javelin, from the moment it leaves the thrower's hand until it hits the ground, the best description is that the potential energy is at its highest when the javelin is released. This energy is gradually converted to kinetic energy as the javelin moves through the air. When the javelin hits the ground, the kinetic energy is then dissipated.