Final answer:
An unrestrained driver suffering a heart contusion during a car crash would experience this during the organ collision phase, which is the secondary internal impact where organs hit the body's interior structures.
Step-by-step explanation:
The injury mentioned, a contusion to the heart, would have occurred during the organ collision phase of the accident. The organ collision is the second impact within the body, where the organs hit the inside of the body, often against the ribcage or skeletal structure. A car crash typically involves three collisions: the vehicle collision, where the car impacts another object; the body collision, where the person's body hits an object inside the car, such as the steering wheel or dashboard; and finally, the organ collision, which can cause internal injuries such as the contusion described.