By analyzing the measures of student success in learning the fundamentals of physics in conjunction with the research reported in the literature one can conclude that it is difficult or undergraduates as well as high-school students to gain a reasonable understanding of elementary mechanics. Considerable effort has been devoted to identifying those factors which might prevent mechanics being successfully learnt and also to developing instructional methods which could improve its teaching (Champagne et al. 1984, Hewson 1985, McDermott 1983, Saltiel and Malgrange 1980, Whitaker 1983, White 1983). Starting from these research results and drawing from their own experience (Borghi et al. 1984, 1985), they arrived at the following conclusions. A strategy based on experimental activity, performed by the students themselves, together with a proper use of computer simulations, could well improve the learning of mechanics and enhance the interest in, and understanding of, topics which are difficult to treat in a traditional way. The authors describe the strategy they have designed to help high school students to learn mechanics and report how they have applied this strategy to their particular topic of projectile motion.