If a dog is hit by a car and the internal organs bleed heavily, it will die within about a day. If the dog is hit by a car but the internal organs do not bleed, it may not die. Generally, if a dog is hit by a car, it will cause internal visceral rupture or internal bleeding. Rupture will cause hemoperitoneum and excessive blood loss, leading to shock or death of the dog. It depends on the degree of damage to the internal organs and whether there is bleeding in the internal organs. It is best to go to the hospital for examination to avoid life-threatening injuries.