Final answer:
The question involves a Physics problem related to the conservation of momentum in a collision between two vessels and the subsequent injury of driver B, with an emphasis on the severing of a blood vessel and medical response to such trauma.
Step-by-step explanation:
Traffic Collision and Resulting Injuries
When discussing a scenario in which two vessels collide and driver B is injured, the subject matter falls under Physics, particularly the study of momentum and collisions. The collision described involves a small car and a truck which, after impact, lock together. To calculate the velocity of the combined wreckage, you'd apply the conservation of momentum, meaning the momentum before the collision equals the momentum after the collision because momentum is conserved in the absence of external forces.
If driver B is injured and a blood vessel is severed, this raises concerns in medicine or health sciences. In the event of severe bleeding, emergency medical care is needed to control the loss of blood and to prevent further complications. The injuries sustained and their treatment involve both emergency response protocols and knowledge of the circulatory system, which includes understanding how to manage trauma and administer appropriate medical intervention such as blood transfusions.