Mechanical engineering encompasses a wide range of topics beyond classical mechanics, including heat transfer, thermodynamics, fluid mechanics, and material properties. Different specialties within mechanical engineering, such as HVAC system design or automotive engineering, require the application of various physics principles tailored to specific projects. While some may wonder if mechanical engineers engage with modern physics concepts like elementary particle physics, such applications are rare and typically involve collaboration with physicists, particularly in specialized fields like particle accelerator design. Overall, the field is diverse, and the specific physics involved depends on the engineering focus.