The aim of this research was to explore students' application of theoretical knowledge in real-life situations using pulley systems in a competition designed for primary school students. The study was conducted with 24 primary school students who had completed year seven, and who volunteered to participate in a summer science camp. In groups, the students were asked to design and build a pulley system using selected equipment that would hold a load of 100 grams in balance or raise it with minimum force. This was to be achieved within a time limit of 30 minutes. During the activity, the students first attempted to use the theoretical knowledge taught at their schools and designed a theoretical diagram. When they attempted to apply the diagram using real equipment, they realised that different factors (for example, pulley weights, friction, etc.) were present. Thus, they realised that the procedural problems they solved in the classroom about pulleys were different from real life.