In this experimental study, natural rock pieces as well as concrete balls and cubes having imbedded accelerometers in them were made to fall and roll over a 45m high natural slope composed of exposed rocks and vertical planes in an attempt to elucidate further the mechanism of rock fall movement along the slopes and the energy associated with the movement. As a result the following points were mainly clarified: 1) flight and collision are the main forms of the rock fall movement; 2) collision causes ground destruction, thereby resulting in loss of energy, so the bouncing velocity becomes the critical velocity; 3) bigger the size of the falling rock piece, higher the falling velocity; 4) when bounced from a gentler portion of the slope, the flight time becomes longer with greater bouncing height and larger colliding velocity; 5) the reduction rate of velocity is high when the angle of collision is small; 6) equivalent friction coefficient changes with the falling movement; and 7) the geometric configuration of the slope governs the amount of bouncing height. (author abst.)