# Simple collision between two moving bodies.

Truck and car collide in one dimension. Assume same velocity. I see this as having 4 forces, two on each body.

Each vehicle exerts its own force on the other. The truck exerts a force on car and vice versa. In addition, the truck's exertion of force on the car is reacted to via newton's third law. and the car's exertion of force on the truck is reacted to via newton's third law.

Taking the car individually, it has the force from the truck acting on it. Plus it has the reaction force from having acted upon the truck.

I suspect that my logic is flawed but I cannot see why. Should I treat each body's forces as though it slammed into a wall? You slam into the wall, exerting a force on it, whereupon the wall returns the favour. It just seems different to me. The vehicle has velocity whereas a wall does not.

Confused

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ehild
Homework Helper
Hi whammer, welcome to PF.

When two bodies A and B interact, moving or not moving, A exerts a force FAB to B, and B exerts the force FBA to A. The forces are of equal magnitude and opposite direction. So there is only one force acting on a body. The reaction force a body exerts acts on the other body, not on itself.

ehild

Truck and car collide in one dimension. Assume same velocity. I see this as having 4 forces, two on each body.

Each vehicle exerts its own force on the other. The truck exerts a force on car and vice versa. In addition, the truck's exertion of force on the car is reacted to via newton's third law. and the car's exertion of force on the truck is reacted to via newton's third law.

Taking the car individually, it has the force from the truck acting on it. Plus it has the reaction force from having acted upon the truck.

I suspect that my logic is flawed but I cannot see why. Should I treat each body's forces as though it slammed into a wall? You slam into the wall, exerting a force on it, whereupon the wall returns the favour. It just seems different to me. The vehicle has velocity whereas a wall does not.

Confused