反作用力(物理高人請進)

The main reason is that the mass of a car is much smaller than the mass of a truck, thus the car suffers a greater change of velocity during collision.

Since during an impact, the force and time duration acting on both the car and truck are the same, that is to say, they both suffer from the same 'impulse' (impulse = force x time)

But impulse = change of momentum = mass x change in velocity
Because the changes of momentum of the car and truck are the same, one with smaller mass (the car) will have a greater change in velocity than one with larger mass (the truck).

This sudden rapid change in velocity of the car not only gives severe impact to passesngers but also gives serious damage to the car because of inertia.

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