Mechanics / forces / momentum
The Truck and the Car Feel the Same Force
That the truck exerts a bigger force on the car than the car does on the truck, because the car comes off worse. The damage difference is real; attributing it to unequal forces is the single most reliably held wrong belief in the Force Concept Inventory.
In any collision the two bodies exert equal and opposite forces on each other, always. What differs is the acceleration each force produces — the car, with less mass, changes velocity more, and that is what wrecks it.
The lesson that sent you here
- Motion Does Not Require a Force
That a moving object must have a force acting on it, and that when the force is 'used up' the object stops — the medieval impetus theory, which most students hold walking into their first mechanics class and many still hold walking out.
1 published lesson depends on this concept, which is what moves it up the writing queue. Nothing is hidden behind this page — it has not been written.