# How much speed would it lose? **URL:** \ **Category:** Factual Questions\ **Created:** [November 10, 1999, 7:24pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632 "1999-11-10T19:24:00Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![robespierre](https://avatars.discourse-cdn.com/v4/letter/r/9dc877/32.png) [@robespierre](https://boards.straightdope.com/u/robespierre)\ **Post date:** [November 11, 1999, 6:44am UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/1 "1999-11-11T06:44:00Z")
Ok, this has been troubling me, but I have not, for obvious reasons tried it in reality. Say you have nice heavy powerful automobile, say a mid 60’s car, about 4000lbs with about 400hp. At highway speeds (65mph), if it were to strike another vehicle, but a much, much lighter one, (no more than 2000lbs) that travelling slower(35mph), or hell even stationary, what would happen? (Assuming that no movie type crap happened ie. instant explosion, lost control, flying through the air…) I doubt it would stop completely, but just how much speed would it lose? * * * I can solve any problem! Just give me a rifle and a clocktower! ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [November 10, 1999, 7:24pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/2 "1999-11-10T19:24:00Z")
- - - A buddy in the service was in Germany and took a few pictures of wrecked cars (in junkyards) that had been in accidents - ones that got on the autobahn going the wrong way. Usually if they hit head on, what happens is that one car “slides” up and over the other. Both cars end up flattened and ripped open. Usually _totally_ unsalvageable - when you get into a head-on collision and both rear wheels are ruined, you know you hit pretty hard (if you’re still around to know, that is). He had one photo of a pile of cars in a junkyard; you really couldn’t tell where one car started and another began. - MC ---
**Author:** ![metroshane](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@metroshane](https://boards.straightdope.com/u/metroshane)\ **Post date:** [November 10, 1999, 7:35pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/3 "1999-11-10T19:35:00Z")
It’s impossible to calculate with out knowing if the second car has there brakes on, or how much damage is done in the collision. but say no damage… 1st car \>\>\> 65 mph x 4000lbs = 260,000 metroshanes of force. 2nd car \>\>\>\>\>\> traveling in same direction 35 mph X 2000lbs = 70000 metroshanes a difference of 190000 metroshanes. 190000 divided by 4000lbs = 47.5 mph difference I could be seriously wrong. * * * I treated Art as the supreme reality, and life as a mere mode of fiction–Oscar Wilde ---
**Author:** ![Nickrz](https://avatars.discourse-cdn.com/v4/letter/n/bbce88/32.png) [@Nickrz](https://boards.straightdope.com/u/Nickrz)\ **Post date:** [November 10, 1999, 7:46pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/4 "1999-11-10T19:46:00Z")
I have performed the above experiment, albeit at a slower speed (55 mph) and a lighter vehicle ('89 Plymouth Voyager Minivan hereinafter referred to as V1). The other test vehicle was a '92 Nissan Pathfinder SUV (V2). We don’t have a weight handy for either participant. V2 was travelling very slowly (through a red light) at a right angle perpendicular to and in front of V1. V1 struck said vehicle squarely behind the driver’s door, tipping V2 completely onto its side. V1 came to a complete stop shortly thereafter (on the order of a few measly microseconds). I’m sure you can extrapolate this data to fit your particular scenario. Collisions between vehicles of differing weights at speeds on the order of 65 mph generally result in rapid decelleration and complete cessation of all motion by both parties. ---
**Author:** ![metroshane](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@metroshane](https://boards.straightdope.com/u/metroshane)\ **Post date:** [November 10, 1999, 7:46pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/5 "1999-11-10T19:46:00Z")
Wait, second car, opposite direction. * * * I treated Art as the supreme reality, and life as a mere mode of fiction–Oscar Wilde ---
**Author:** ![Konrad](https://avatars.discourse-cdn.com/v4/letter/k/f475e1/32.png) [@Konrad](https://boards.straightdope.com/u/Konrad)\ **Post date:** [November 10, 1999, 8:06pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/6 "1999-11-10T20:06:00Z")
Robespierre: It would lose 10 mph. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [November 10, 1999, 11:58pm UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/7 "1999-11-10T23:58:00Z")
US SUVs now have special bars in the front so they won’t run on top of the vehicle in front. ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [November 11, 1999, 10:25am UTC](https://boards.straightdope.com/t/how-much-speed-would-it-lose/4632/8 "1999-11-11T10:25:00Z")
- - - I kinda doubt it helps much, really. I mean, I’m not saying _you’re_ full of it, handy; I’m saying that this is a solution from the same bright companies that install “light bars” in pickup trucks now instead of roll bars. - I tend to think most of the solution was when manufacturers stopped using leaf-spring suspensions in truck front ends. Many still use them in back, but no US trucks use them in the front anymore. (even Jeeps!!! how _revolting!!!_) Kits for raising independent front suspensions are _way_ more expensive than the ones for leaf springs, so less people do it nowadays. It’s been quite a few years since I’ve seen a new truck with a 12" lift and 44-inch tires. - MC