Help Needed: Calculating Speed After Motorcycle Accident

In summary, Andre, a man from South Africa, is seeking assistance in determining the speed at which he was traveling during a motorcycle accident. He has provided some details, including the point of impact, launch point, his weight, and the distance he rolled after the collision. However, without a picture or drawing of the situation, the calculations are inconsistent and inconclusive. The estimated speed at impact is approximately 6.859 m/s, but there is missing data for the initial vertical motion caused by rotation at the point of impact. The only conclusion is that the motorcycle was likely traveling at a speed higher than 6.859 m/s, but without more consistent data, no further conclusions can be drawn.
  • #1
bikerguy
3
0
Hi there Ladies and Gentlemen. My name is Andre, and I am from South Africa and would like if someone could assist me.
Im going to admit that maths is not my forte and I am lost when it comes to anything more than plus or minus or times. lol
I was in a motorcycle accident recently , and after spending months in hospital, I now face the Court cases. I would like someone to help in finding one thing: What speed was I traveling upon collision?

Point of impact to where I came to contact with tarmac, is 12m
Hight of launch point is 1.2m above contact point
I weigh 109 kilograms
i rolled another 3m
Launch angle is between 10 to 20 degrees, although, this is the general estimate found on the internet.

if anyone can help, it would be appreciated, as i cannot afford an attorney, and I will have to make my own representation in court.

Thank You!
 
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  • #2
It would greatly help the analysis if you could please post a picture or drawing of the physical situation, with labels for everything you know.
 
  • #3
Ackbach said:
It would greatly help the analysis if you could please post a picture or drawing of the physical situation, with labels for everything you know.

HI Ackbach, here is what i know
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  • #4
I've done a couple of checks on this and the only thing I can think of is that your numbers are inconsistent.

The sliding part is pretty decent. I couldn't get any sort of "rolling friction" data so I had to assume that the rider is sliding. This would imply a speed greater than that predicted by rolling, but I can't say by how much. Anyway the estimate of the horizontal component of the velocity at impact will be \(\displaystyle \sqrt{6 \mu _s g} \approx 6.859~\text{ m/s}\) using a hybrid guess of \(\displaystyle \mu _s = 0.8\). The guess comes from an eyeball judgement of 4 different surface combinations that I thought were relevant.

So far so good. Now for the projectile part of the motion. To do this properly the initial vertical motion is caused by a rotation of the motorcycle at the point of impact with the truck. I need the horizontal distance from the back of the truck to where the rider is sitting and the vertical distance from the back of the truck to how high the rider was sitting. Without this information we have to confine ourselves to a consistency check on the speed found from the sliding part of the motion.

Again we are missing data. The simplest way to continue here is to assume that h is about 1.5 m. But that is where this all goes to Hades. I'm taking the horizontal component of the velocity at the point of impact to be our previously calculated 6.859 m/s and we need to find an initial vertical component of velocity. This comes in at more than 19.795 m/s, which implies an angle some 70 degrees. But this angle has to be less than the 15 degrees you are estimating.

The only conclusion I can draw is that the speed the motorcycle hits the truck with is significantly greater than the predicted 6.859 m/s (15.3 mph). Without more consistent data that's all I can say.

-Dan
 
  • #5
topsquark said:
I've done a couple of checks on this and the only thing I can think of is that your numbers are inconsistent.

The sliding part is pretty decent. I couldn't get any sort of "rolling friction" data so I had to assume that the rider is sliding. This would imply a speed greater than that predicted by rolling, but I can't say by how much. Anyway the estimate of the horizontal component of the velocity at impact will be \(\displaystyle \sqrt{6 \mu _s g} \approx 6.859~\text{ m/s}\) using a hybrid guess of \(\displaystyle \mu _s = 0.8\). The guess comes from an eyeball judgement of 4 different surface combinations that I thought were relevant.

So far so good. Now for the projectile part of the motion. To do this properly the initial vertical motion is caused by a rotation of the motorcycle at the point of impact with the truck. I need the horizontal distance from the back of the truck to where the rider is sitting and the vertical distance from the back of the truck to how high the rider was sitting. Without this information we have to confine ourselves to a consistency check on the speed found from the sliding part of the motion.

Again we are missing data. The simplest way to continue here is to assume that h is about 1.5 m. But that is where this all goes to Hades. I'm taking the horizontal component of the velocity at the point of impact to be our previously calculated 6.859 m/s and we need to find an initial vertical component of velocity. This comes in at more than 19.795 m/s, which implies an angle some 70 degrees. But this angle has to be less than the 15 degrees you are estimating.

The only conclusion I can draw is that the speed the motorcycle hits the truck with is significantly greater than the predicted 6.859 m/s (15.3 mph). Without more consistent data that's all I can say.

-Dan

Thank You Dan,
Perhaps this can help?

Studies show that the coefficient of friction between the operator’s clothing and the roadway surface for cotton/ wool and polyester is between .7 to .85 g’s and for leather is between .6 to .7 g’s. When a body does not slide but tumbles the coefficient of friction is approximately 1.0 or higher. There may be a combination of sliding and tumbling so the slide to stop coefficient of friction may vary

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FAQ: Help Needed: Calculating Speed After Motorcycle Accident

1. What is the formula for calculating speed after a motorcycle accident?

The formula for calculating speed after a motorcycle accident is: speed = distance/time. This means that you need to divide the distance traveled by the motorcycle by the time it took to travel that distance. This will give you the average speed of the motorcycle during the accident.

2. How do I determine the distance traveled by the motorcycle during the accident?

To determine the distance traveled by the motorcycle during the accident, you will need to gather information such as the skid marks on the road, the point of impact, and any other physical evidence. You can then use this information to calculate the distance traveled using the formula: distance = speed x time.

3. What units should I use when calculating speed after a motorcycle accident?

The units used to calculate speed after a motorcycle accident should be consistent. For example, if you are using meters for distance and seconds for time, then the speed will be in meters per second. It is important to use consistent units to ensure accuracy in your calculations.

4. Can I use the speedometer reading to determine the speed of the motorcycle during the accident?

In some cases, the speedometer reading can be used to determine the speed of the motorcycle during the accident. However, it is important to note that the speedometer reading may not always be accurate, as it can be affected by factors such as tire pressure and calibration. It is best to use a combination of methods, such as physical evidence and calculations, to determine the speed.

5. How can I use the calculated speed after a motorcycle accident in my analysis?

The calculated speed after a motorcycle accident can be used in various ways in your analysis. It can help determine the severity of the accident, the potential injuries sustained, and the cause of the accident. It can also be used to compare the speed of the motorcycle to the speed limit of the road, which can be helpful in determining if the rider was driving recklessly or not.

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