Does anyone know the reason why:( dryer pops the breaker as soon as the button for start is pushed?

You have a short somewhere. You are going to have to open unit up and do some checking. Check the start switch, the heating element (most likely) and motor. Check the switch and element. Unplug unit from power source. Remove one wire from each componet checking and check for continuity. Good Luck and post back with results.