Calculate vehicle speed based on impact results?

AI Thread Summary
Calculating the speed of the other driver (OD) in a collision involving a 2003 Hyundai Elantra and a 2005 Nissan Titan requires detailed information about the impact dynamics. Key factors include the curb weights of both vehicles, the nature of the impact on the Titan's passenger side rear axle, and the resulting spin and lift of the truck. The absence of braking and the specific conditions of the road, such as temperature and surface type, also play a crucial role in the analysis. Additional details needed for a more accurate calculation include weight distribution, tire friction coefficients, and the extent of vehicle deformation during the collision. Understanding these elements is essential for a precise estimation of the OD's speed at the time of impact.
Tom Brokaw
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I hope I'm not asking too much.

Other Driver hit Family Member. I want to calculate how fast OD was going. Desired results would be accurate to within 5 MPH or less.

OD was in a 2003 Hyundai Elantra; googled curb weight around 2700.
FM was in a 2005 Nissan Titan; googled curb weight around 5000.
Impact was on passenger side rear axle of the Titan.

Titan was spun approximately 180 degrees and passenger side was lifted off the ground. I'm don't have specifics on that yet, such as did the curb stop the spin and therefore cause the truck to start a rollover, or did the impact generate the lift and the spin came to a "natural" stop? Police report indicates the Hyundai scraped the road, causing damage to the street surface. I don't have more specific info than that.

Dry asphalt. Almanac.com provided the following temps on the day in question:
Minimum
37.4 °F

Mean
41.4 °F

Maximum
48.2 °F

The accident occurred on a March afternoon in a northern latitude an hour prior to sunset, so temps should not have fallen too much.

I'm sure more info is needed but I don't know enough to know what that is. Any help appreciated.
 
Physics news on Phys.org
Accident investigations are very complicated. Energy is lost to deformation of the cars. Momentum is lost unless you include the relatively tiny effects on the relatively massive earth. How much energy is consumed by the brakes and tires depends on how much braking was involved and how much sideways sliding was involved.
 
Thanks for the reply.

No braking was involved. The only sliding that I'm aware of is the arced motion of the rear truck wheels.

What other info should I gather? Or is there simply too much?
 
There are a lot of details involved. Weight distrubtion of the vehicles, coefficient of friction for the tires, did the tires hop or did other body parts of the car scrape the ground which would affect friction coefficient. I'm not sure how suspension plays a roll in the reaction to a collision. How much deformation occurred, ...
 

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