How can homologous structures be used as evidence for shared common ancestry?

Homologous structures are structures that are similar in related organisms because they were inherited from a common ancestor. These structures may or may not have the same function in the descendants. They all have the same basic pattern of bones. They inherited this pattern from a common ancestor. However, their forelimbs now have different functions

When the ball is rising up, it gains kinetic energy. when the ball reaches the very top, it will have all potential energy, until it falls back down and gains it kinetic energy. finally when you catch the ball or it falls back down, it would have gained its potential energy back.