a truck pushing started and converted gasoine into light and vision matter & kerosene is a sink of physical matter ->  a car engine started and converted the chemical energy in gasoline into heat and sound energy  a car engine started and converted the chemical energy in gasoline into heat and sound energy & vision is a mean of mechanical matter ->  a car engine usually converts chemical energy into mechanical energy and heat energy  a car engine usually converts chemical energy into mechanical energy and heat energy & when zero mean of matter points into another mean of matter , the flood glass of matter is variable -> when the car engined started the total amound of energy is constant