When the bullet stops this energy goes to zero, as the energy must be conserved the work done by the head of the superhero must be equal to the original energy of the bullet:
W= K
Considering an average constant force, the work can be calculated as:
Your organs are working together to control and keep your body moving!! When a organ starts to do they're job it may need some other organs to help. When this happens it begins the Organ System!