Calculate vehicle speed based on impact results?

  • Context: Undergrad 
  • Thread starter Thread starter Tom Brokaw
  • Start date Start date
  • Tags Tags
    Impact Speed Vehicle
Click For Summary

Discussion Overview

The discussion revolves around calculating the speed of a vehicle involved in an accident based on the impact results. Participants explore the complexities of accident reconstruction, including the physical characteristics of the vehicles, the nature of the impact, and the conditions at the time of the accident.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes the complexities of accident investigations, mentioning energy loss due to vehicle deformation and the need to consider momentum, including the effects on the earth.
  • Another participant specifies that no braking occurred during the accident and that the only sliding involved was from the arced motion of the rear truck wheels.
  • Concerns are raised about the need for additional information, such as weight distribution, coefficient of friction for the tires, and the role of vehicle suspension in collision dynamics.
  • Discussion includes the potential impact of the vehicles' weights and the specific conditions of the road surface on the calculations.

Areas of Agreement / Disagreement

Participants express uncertainty about the necessary details for accurate calculations, indicating that multiple factors need to be considered. There is no consensus on what specific information is required or how to approach the calculations.

Contextual Notes

Limitations include missing assumptions about vehicle deformation, the exact nature of the impact, and the influence of environmental conditions on the calculations.

Tom Brokaw
Messages
2
Reaction score
0
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, ...
 

Similar threads

Undergrad Is the Collision Formula Provided Accurate for Low-Speed Vehicle Impacts?
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Can anyone estimate the speed of a vehicle in a car accident without skid marks?
  • · Replies 4 ·
Replies
4
Views
3K
Calculating Vehicle Speed based on Downforce (Aerodynamics)
  • · Replies 8 ·
Replies
8
Views
5K
Speed of each vehicle after the collision?
  • · Replies 1 ·
Replies
1
Views
2K
What if Gravity could be controlled?
  • · Replies 1 ·
Replies
1
Views
4K