There is growing recognition that young children are familiar with nai\"ve physics, and construct their own theory about the natural world from early childhood. The research reported in this study focuses on intellectual play activities involving pendulums carried out by young children at a kinder - garten in Japan. Over the course of three weeks, five-year-old children partic - ipated in these pendulum play activities. They made pendulums by themselves, tried them out, compared them with others, identified variables in moving, controlled these variables, and communicated their findings with others in the context of free guided play. Throughout these activities, the children changed their sense making of pendulums as objects of art to objects for investigation. Simple equipment, such as weight balances and counters, seemed to develop their scientific and technological competency. Their findings were displayed on a communication board so that they could appreciate and discuss them with each other. Socio-cultural aspects of science and technology in our glob - al society are coming into the spotlight in the field of science education. Drawing on recent reviews, this paper proposes some implications in relation to the theory and practice of science activities for young children that aim to develop their scientific, technological, and social competency in early child - hood.