What would be three collisions in one crash?

Question

In physics, during a "car accident, three collisions occur during one crash. If someone were to crash into a tree, what would be three collisions in that crash. Explain.

 

FIRST COLLISION:

 

SECOND COLLISION:

THIRD COLLISION:

 

Thank you.

Answer 1

Let's take the car crash example (car into car). In this crash, the car first comes to a stop after colliding with the other car (1st collision). By Newton's First Law, the person's body was traveling at the same speed as the car and has no force acting on it yet, so it continues moving forward at that original speed even after the car has stopped. This carries the person's body forward until it collides with the seatbelt and airbag (2nd collision). The seatbelt and airbag then exert a force on the body, decelerating it — but the internal organs are only loosely connected to the skeletal structure, so they're still moving at the body's original speed even after the body itself has stopped. This causes the organs to continue moving until they collide with the skeletal structure and surrounding tissue (3rd collision).

In the case of colliding with a tree, only the object of the first collision changes — the underlying physics of the second and third collisions stays the same, since both depend on inertia carrying an object forward once whatever is ahead of it has already stopped. First, the car collides with the tree and comes to a sudden stop. The person's body, still carrying its original speed, then collides with the seatbelt and airbag (2nd collision). Finally, once the body has been decelerated by the seatbelt and airbag, the internal organs — still moving at that same original speed — collide with the now-stationary skeletal structure (3rd collision).