A powertrain includes an electromechanical transmission mechanically-operatively coupled to an internal combustion engine and an electric machine adapted to selectively transmit mechanical power to an output member through selective application of a plurality of clutches. This golf club head includes a rib which extends from the toe side to the heel side in the sole portion, and a weight portion which is provided in the sole portion on the back side with respect to the rib, and increases the amplitude of vibration of the sole portion. They are also easy to manufacture and provide fast and accurate reading over a wide range of inclination angles of up to 360\xb0.