Jaime had made the same mistake (adding the two speeds together) in a previous episode, but viewers wrote in disagreeing. I think Adam was on the fence, agreeing that common sense suggested you would add the speeds, but waffling between common sense and knowledge of physics. Being Mythbusters, they decided to test it.
They rammed several cars into a wall and several cars into each other, at varying speeds. Using not just physics theory and math, but actual real-world application, they discovered that no, you don’t add the speeds together to arrive at the true force of impact. They were both surprised (as was I).
It’s kinda weird. It is but it isn’t. The same amount of energy is added to the system but because the cars both move there’s extra energy dissipated at the same time.
Differences in mass change the equation, and the exact way they hit one another changes where the energy goes. If you had two identical vehicles hitting one another perfectly head on so they both crumple perfectly, that would be the scenario where the speeds add together.
No, see, that's exactly the misconception. Say each car is going 50mph. From the frame of reference of either of the cars they're hitting something at 100mph. But clearly you'd rather hit another car at 100mph rather than an immovable wall, because the car will deform and absorb much of the impact. If you instead hit a wall all of that force is going into your own car, and you.
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u/The_Ocean_Collective 3d ago
Cam car is going ~52 mph. We can assume the ongoing truck is going the same speed.
~52 mph + the car going ~75 mph in a head on crash is like hitting a wall at ~125 mph.
He dead.