Check for symmetries. If a system is invariant under translation, momentum is conserved. If it’s invariant under rotation, angular momentum is conserved. C. The Lagrangian Approach (Advanced)
Once you understand the solution, put it away and try to derive the entire result from scratch the next day. Summary Table: Mechanics Problem Difficulty Contest Level Focus Areas Recommended Resource Intro (F=ma / NSEP) Kinematics, Newton's Laws AAPT Archives Intermediate (USAPhO) Rigid Body Rotation, Thermodynamics David Morin’s Problems Advanced (IPhO / APhO) Relativistic Mechanics, Lagrangians IPhO Past Papers Conclusion Check for symmetries
Master Classical Mechanics: Physics Problems and Solutions for Olympiads and Contests Check for symmetries