Abstract: The essence of education is to cultivate students' ability of thinking and solving problems. Mechanics courses emphasize basic concepts, theories and methods, but there are many concepts and formulas in the course, which is one of the most difficult courses in engineering. Some enlightening cases can be designed in lessons, which are not only related to the knowledge students have learned, but also vivid, interesting and philosophical, so that students can understand how to apply abstract theory in practice, how to deal with complex problems and obtain wisdom beyond knowledge. This paper introduces the phenomena in cycling, high jump and diving, and explains the mechanics principle behind these phenomena from the angle of reference system, center of mass motion theorem and the conservation of the moment of motion, as well as the enlightenment to us.