Which of the following structures collects the depolarization wave from the atria to pass it onto the ventricles?

After the depolarization wave front passes through the atria, it enters that AV node which is located at the apex of the triangle of Koch. It would be the AV node that collects the depolarization wave from the atria to pass it onto the ventricles. Hope this answers the question.

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.