The term 'Newtonian Topic' refers to the laws of motion and gravity proposed by Sir Isaac Newton in the 17th century. INERTIA, which is a seven-letter word, is one of the main concepts of Newtonian physics. It is defined as the tendency of an object to remain at rest or in uniform motion unless acted upon by an external force. INERTIA is an important concept in Newtonian physics, as it explains why objects continue to move in a straight line unless acted upon by an external force.