A person with hep b cuts themselves on a knife and leave traces of blood...i use that knife to cut my food up and eat said food....will i get hep b?

Maybe. There are reports of Hep B surviving for months in a needle stick causing an infection in a worker cleaning out a crack house. Though a different type of exposure it does suggest this virus is quite tolerant of outside exposure for a lengthy period. The person with Hep B would need to be in the active infection phase with circulating virus to be a risk. Many are dormant.