3 ms·
Moving some vectors around to make it look more similar - would I like to hit a nice solid wall at 60MPH or a parked car head-on at 120MPH. The head-on collisi
by dedward 16y ago
Moving some vectors around to make it look more similar - would I like to hit a nice solid wall at 60MPH or a parked car head-on at 120MPH.
The head-on collision has twice as much energy to dissipate, and introduces all kinds of projectiles and other stuff heading in my direction. I'll take the wall over the car.
- modeless 16y agoYour first paragraph is wrong. You can't switch frames like that because in a collision both cars will quickly come to rest relative to the ground, so kinetic energy in the ground frame is what matters. A car at 120 MPH has 4 times the kinetic energy of a car at 60 MPH, not 2 times, because kinetic energy increases as the square of velocity. I'll agree with the projectile thing though.
- RiderOfGiraffes 16y agoNot entirely true. After colliding with a stationary car the previously moving car will retain some of its velocity. That will then dissipate over time and be less violent. So to some extent - when simplified, to a first approximation - you really can switch frames of reference like that.
- modeless 16y agoWhen simplified, yes, but if you start talking about projectiles then you are explicitly not simplifying things, and should also account for the effect of the ground because it's probably a larger concern than projectiles in a collision like this.