By doing so, weld current and force is focused into the small area of the projection, and heat is obtained from the resistance to the flow of the welding current. Due to this heat, the projections collapse and the parts are weld together. Another successful welding technique is capacitor discharge stud welding, which uses weld studs or specially formed bolts for welding instead of projections.
Definition of inert. 1  1 : lacking the power to move. 2  2 : very slow to move or act : sluggish. 3  3 : deficient in active properties; especially : lacking a usual or anticipated chemical or biological action.
That is called inertial and the first law of motion is also known as the law of inertia. Inertia is defined as the tendency of an object to remain at rest or of moving until an external force acts on it. Object having heavier mass has larger inertia. The mass of an object is a measure of its inertia.