The idea was that if one slides the object off of the table, the energy will return when it hits the floor. Let s look at this logic. Let s say that we are watching television and Mary leaves the room. Another person responds that she will return. Energy cannot be potential, perhaps, or maybe.
Energy is and it has to be somewhere.
Let the initial displacement angle be 90 degrees. This above rectangle represents this bob in a free falling system. In this case, the bob swings down to nadir. Ergo, a triangle is a better representation of this swinging system. This representation is not accurate because the bob does not move in a straight line as indicated by the hypotenuse of the triangle.