What are the main differences between an undergraduate degree in physics and one in engineering (say, mechanical)? It will be extremely helpful if someone can detail the four-year course structure and plan for each of them.
Pick any school or schools, visit the web pages for their Physics department and Mechanical Engineering department, and compare the degree requirements/sample course plans/curricula.
Physics studies the natural universe.
Engineering solves design problems using physics, math, and other science.