Contrary to popular belief the scientific method is a what process, because scientists often have to revisit, repeat or revise previous steps

Contrary to popular belief the scientific method is an iterative process because scientists often have to revisit, repeat or revise previous steps. It is very common for an experiment to be done many times in different international laboratories in order to confirm that a conclusion is valid. All good scientific experiments should allow results to be replicated. 

John applied force to ring the door bell. So it would be contact force. I think