1. Momentum is not a force nor energy, it is a completely independent thing 2. Both p = mv and F= ma is for calculating the effort of changing the speed of an moving object, but the former one do this through comparing the momentum of an object before and after it changes speed while the latter one do this through the object's acceleration. They are just two different methods for achieving the same goal 3. Inertia is a property of an object with mass for being reluctant to change its speed while momentum really quantifies the effort required to change one's speed. Thank you, These clarification would give me a big help!