Can anyone help me figure out how fast a bus was going?

In summary, a 40,000-pound object was traveling at 35 mph when it was hit by a bus traveling at 45 mph, causing the car to launch 7-9 feet forward and rotate 180 degrees. There were no skid marks to measure the bus's stopping distance.
  • #1
stingle
2
0
I don’t know much about physics, but I was recently in an accident and I am trying to figure out approx how fast the other driver was going.
What details would I need for the formula?

I do know the object weighs 40,000 lbs (speed limit in area was 35, so I know it was going anywhere from 35-45 mph)
I was hit with enough force to launch my car (weight 1800 lbs) 7-9 feet forward and rotate it over 180 degrees.

There were no skid marks to measure the bus did stop approx 30 feet after impact.

From the info above is there any way to figure out speed, if not what other info would be needed?

I am not very good at numbers so any input/assistance would be greatly appreciated!
 
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  • #2
Welcome to PF!

stingle said:
I do know the object weighs 40,000 lbs (speed limit in area was 35, so I know it was going anywhere from 35-45 mph)
I was hit with enough force to launch my car (weight 1800 lbs) 7-9 feet forward and rotate it over 180 degrees.

There were no skid marks to measure the bus did stop approx 30 feet after impact. …

Hi stingle! Welcome to PF! :smile:

Sorry, but without skid marks, it's virtually impossible even to estimate the speed. :redface:
 
  • #3
It is possible using physics to determine minimum braking distance, given vehicle mass, velocity, and maximum braking force. However for a situation involving a vehicle collision, there are too many variables and too many assumptions which would have to be made to come to any kind of useful conclusion, let alone one that would stand up in court without experimental data. The best you could come up with would be limits of plausibility (e.g. if the bus driver claimed he only hit you at 2 mph you could prove this is physically impossible due to conservation of momentum).
 
  • #4
Welcome to PF, Stingle.
This subject has arisen before. The only practical approach is to hire a professional accident reconstructionist. Even if we could give you a formula (which we can't), you still need someone who can testify in court and be cross-examined. That is absolutely not in our job description.
 
  • #5
Thanks everyone, I figured as much, but I am not versed in laws of physics. I do appreciate you taking the time to help provide an answer.
 

1. How can I determine the speed of a bus?

The speed of a bus can be determined by taking into account the distance traveled and the time it took to travel that distance. This can be calculated using the formula speed = distance/time.

2. What information do I need to figure out the speed of a bus?

To calculate the speed of a bus, you will need to know the distance traveled, which can be measured using a map or GPS, and the time it took to travel that distance, which can be measured using a stopwatch or a clock.

3. Can I estimate the speed of a bus without using any tools?

It is difficult to accurately estimate the speed of a bus without using any tools. However, you can get a rough estimate by using visual cues such as the time it takes for the bus to pass a certain point and the distance between two points.

4. Can I use the speedometer on the bus to determine its speed?

Yes, the speedometer on the bus can give you an accurate reading of the bus's speed. However, it is important to note that the speedometer may not be as precise as using a GPS or other measuring tools.

5. Is it possible to calculate the speed of a bus after the fact?

Yes, it is possible to calculate the speed of a bus after the fact if you have the necessary information such as the distance traveled and the time it took to travel that distance. However, the accuracy of the calculation may be affected by factors such as traffic and stops along the route.

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