this post was submitted on 05 Apr 2026
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The higher mass and force transmitted by a truck means the human will be thrown further and possible impact other objects at a higher speed
Not all of that energy is transferred. The car doesn't stop as if it hit a wall. Usually it barely slows down. The human on the other hand gains at most the kinetic energy corresponding to their body mass and the speed of a human bouncing forward off the car at around the same speed as the car was going, so a tiny fraction. Of course impact geometry will determine the specifics and pickups suck there too. The important thing about kinetic energy is that it's dependant on the square of the velocity. That's why speed kills. The mass is just a linear relation.
The issue is energy transfer doesn't care about weight of the human, more kinetic energy will impart more speed to the human during the impact impulse. Imagine a solid bowling ball hitting a beach ball vs a plastic hollow bowling ball hitting a beach ball
Partially correct, the speed (technically acceleration) of the human after a collision is limited by the decceleration of the moving object caused by thr human. Since a car and a truck decellerate about the same amount when receiving the counter-acceleration of the human, the force transfer remains similar.
The bowling ball will not slow down in the slightest when is hits the beach ball, accelerating the beach ball up to it's speed.
The plastic ball will lose significant speed hitting the beach ball, decelerating itself significantly as it accelerates the beach ball.
I'm going to pick some easy math speeds/masses for demonstration. 2,000 kg sedan, 4,000 kg pickup and 100 kg human. Starting velocities of 20m/s and 0m/s. An impact/acceleration time of 1s.
The sedan hits a pedestrian with (f=ma) of 40kN. It takes 2kN to bring the human up to 20 m/s. So the sedan will be somewhere around 38kN, or 19m/s at the end of it and the human absorbing 1.8-2kN.
The truck has f=80kN. Same 2kN for the human. So the truck will be somewhere around 78kN or 19.5m/s at the end. With the human absorbing 1.9-2kN
In either case the we talking a difference of 1.8-2kN for the human. Regardless the mass (and total force) of the vehicle, the relatively small human as a maximum force they can absorb. And that maximum force is heavily related to the speed of the larger object.
Not to say trucks/SUVs aren't deadly for other reasons (like where and how the force os transferred)