How does bleeding on the brain happen after a fall?

Multiple ways. During the fall, if the brain is thrust against the boney skull, it can be injured producing a small hemorrhage. A second mechanism, the bridging veins between the dura and the brain are torn producing a subdural hematoma. With lateral skull fracture, the middle meningeal artery can be torn producing an epidural hematoma. With violent falls, traumatic subarachnoid hemorrhages due to arterial tears.