Whiplash injuries are common in rear end collisions. The passenger's head whips back and forth, giving the injury in this type of wreck its name. Whiplash is cervical strain, the stretching and tearing of delicate tissues in the neck such as muscles, nerve fibers, and ligaments. The effect is pain, which is sometimes permanent, and sometimes headaches, dizziness, and ringing in the ears.
Insurance adjusters, trained by their companies to minimize injuries, often react to a cervical strain diagnosis by saying, "Oh, it is only whiplash, nothing serious," or by redefining the injury as a "Minimal Impact Soft Tissue" or "MIST" injury. The thought they and their insurance defense lawyers try to portray, especially to jurors, is that a minimal impact injury can't be permanent or serious, because if the damage to the car wasn't bad, how could injury to the person inside it be bad? And they use the acronym "MIST" to imply that the injury is like a cool morning's mist that will evaporate in the sun.
This is a terribly simplistic and incorrect, even fraudulent, approach to the dynamics involved in a collision. It fails to take into account differences built into each vehicle's platform or chassis. The platforms designed by some manufacturers are relatively soft, allowing more crushing of the vehicle to occur in order to dissipate the crash forces before that force is transmitted to occupants. Occupants of these cars and trucks usually have fewer whiplash injuries than those in vehicles that are stiffer. In stiffer vehicles, more force from the impact is sent through the body of the occupant since it wasn't dissipated during the crushing of as much metal.
If you're looking for a car to buy, you want one that has plenty of metal around you and that is soft enough to absorb the energy of a wreck by crushing appropriately to save you. Check online for safety ratings of cars to avoid serious whiplash injury. You definitely want to avoid it.