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The Engineer's Notebook is a shared blog for entries that don't fit into a specific CR4 blog. Topics may range from grammar to physics and could be research or or an individual's thoughts - like you'd jot down in a well-used notebook.

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Mass, Momentum and Car Crashes

Posted March 29, 2006 9:00 AM by Chris Leonard
Pathfinder Tags: accidents cars mass momentum SUVs

While driving to work today in my mid-size car, I narrowly avoided a head on collision with a Lincoln Navigator. After my heart rate dropped to a reasonable rate, I began to think about what would have happened had we collided. We were both traveling at about 50 MPH, but I have no doubt my car would have been totaled, while the Navigator would have sustained far less damage.

The reason is obvious, while our speed was the same, the Navigator had far more mass and that extra mass would have shifted the energy from the collision into my car. So, following that logic, if I find myself in a similar situation, albeit one where I will not be able to avoid the collision; should I speed up so that my extra speed offsets the SUV's mass? Is this a rational thought? Obviously were I going to hit a brick wall or something like that, that would not give, speeding up would be a terrible idea; but if I hit a vehicle that will give in the right circumstances, does it make sense to speed up? I ask this in theoretical terms and in a situation where my own self-preservation trumps all other concerns.

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#1

Re: Mass, Momentum and Car Crashes

09/14/2006 12:16 PM

No, speeding up will not help. It will not help you because deceleration is what kills you, specifically your internal organs being crushed (assuming you don't sustain any direct injury.) More velocity means more deceleration. It won't help your car because your mass has not changed, you will just take even more damage. The only thing that will really change is that you'll do more damage to the other car.

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Join Date: Oct 2006
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#2

Re: Mass, Momentum and Car Crashes

10/19/2006 11:50 AM

or another way to think about it is that the the kinetic energy that is involved in the crash increases with your speed - (yes, exponetially to the power of 2) - so speeding up would create more energy that would be transferred to the system -your car and the Navigator.

slowing down would decrease the energy and also give more time (and/or distance) for the Navigator to slow down, and maybe a little more time to pray for a miracle or curse the SOB's at Ford that made that Urban Assualt vehicle a reality.

glad you lived to tell about this one...

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