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.
The definition of inert is slow or having no action or power to move. An example of inert is a slug that is standing still. having inertia; without power to move, act, or resist. tending to be physically or mentally inactive; dull; slow.
The definition of inertia is when an object remains still or moves in a constant direction at a constant speed. Inertia will continue unless the object meets some external force. The more inertia an object has, the less the object will change its motion when it meets another force. The ground is the force, the motion, that causes the object to no longer have inertia and to instead stray from its speed and direction.