How to calculate the speed of a vehicle on impact

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  • Thread starter Thread starter Lordtrenchard
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Discussion Overview

The discussion revolves around the feasibility of calculating the speed of a vehicle at the moment of impact with a stationary object, given certain parameters such as the distance traveled by the object, its weight, and the vehicle's model under dry road conditions. The scope includes theoretical considerations and practical implications related to vehicle collisions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether it is possible to calculate the speed of the vehicle based on the provided information.
  • Another participant argues that the information listed, such as the vehicle model and road conditions, may not be relevant for the calculation.
  • It is suggested that knowing how the impact affected the vehicle's speed is crucial for calculating energy exchange during the collision.
  • A participant highlights that the distance traveled by the object post-impact can vary significantly based on its characteristics, such as being a ball on a hard surface versus a dead weight.
  • Forensic evidence indicating where the object first hit the ground could provide useful data for the calculation.
  • Discussion includes the idea that the maximum distance for a given speed would occur if the object was launched at a 45-degree angle and that the object's center of gravity could affect the distance traveled.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of the provided parameters for calculating the vehicle's speed, indicating that multiple competing perspectives exist without a consensus on the approach to take.

Contextual Notes

Limitations include the need for additional details about the object's behavior post-impact and the potential influence of various factors on the distance traveled, which remain unresolved in the discussion.

Lordtrenchard
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A friend posed this question to me tonight.

If a vehicle hits a stationary object and you know the distance traveled of the object, the weight of the object, the model of the vehicle and that conditions were dry on a tarmac road, is it possible to work out the speed of the vehicle on impact?
 
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280 views and no reply?? Is it possible to calculate?
 
What, no answer in all of an hour and half? There simply isn't enough (and most of what you listed, the model of the vehicle, the condition of the road,etc., is not relevant). Even assuming a "perfectly elastic" impact, you would need to know, for example, how the impact affected the speed of the vehicle- so you could calculate the exchange of energy.
 
Sorry mate. Was just trying to help out a friend who had property damaged in an RTC. Was just asking if it was possible to get a calculation of whether the vehicle was traveling over the 30Mph limit when it hit his property.
 
The key problem is knowing what would have limited the distance travelled.
If the object is a ball on a hard level surface, it could travel 100s of metres without too much encouragement.
If, at the other extreme, it was a dead weight that would not be likely to slide or bounce very far then you can put a lower limit on the speed.
Of course, if there is forensic evidence to show where the object first hit the ground, as a distance from the impact location, that will do instead.
The greatest distance for a given speed would correspond to the object's having been launched at 45 degrees to the horizontal. The distance will also be greater if the object had a higher centre of gravity when struck than when it landed.
Can you fill in some of these details?
 

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