Cut an apple in two parts with inertia
Secure a long sharp knife like as a carving knife. Cut into the apple with the knife unless you can pick them up together. Be sure to have enough of the end of the knife sticking out to enable you to strike it. Now hold knife and apple securely in single hand and strike the end of the knife a sharp blow with a stick. The knife will move by the apple because of the inertia of the apple.