Calculating Weight Increase in Car Crash: 12 Stone Occupant at 30mph

[Simo43]

1. Can you be of any help, I need a simple (if that is possible) equation to help
me determine the weight increase of a 12 stone occupant of a car doing 30mph
coming to a dead stop?




2. Don't have a clue



3. This is a very general question to put into a slide show presentation on Road Traffic Accidents, you may have to dumb down a bit but any help is appreciated.

 

[Uku]

The traveling persons weight as such does not increase (talking non-relativistic speeds), rather his momentum.

 

[Simo43]

Thank you for that but its not what I meant, I realize that there are many forces which act on a body on impact I was looking for something to work out the max weight that will as you say with the momentum of a 30mph dead stop will tear out a passenger seat from its floor mountings, say rated to 50st max.

 

[Uku]

Well, I have yet to see a car where the seatbelt is connected to the chair, usually (in European cars) I see them connected to the cage frame.
As I see it applied, there is usually a stopping distance. If you take the stopping distance to 0, then all the kinetic energy is applied to the person via the seatbelt (no work is done), and that is not the real case.
Check out the examples here:

http://hyperphysics.phy-astr.gsu.edu/hbase/seatb.html
http://hyperphysics.phy-astr.gsu.edu/hbase/carcr2.html#cc1

You can use the work equation:
[tex]W=\Delta E_{kin}=E_{kin2}-E_{kin1}=-E_{kin1}[/tex] since the car is stopped.

Now on the other hand
[tex]W=Fs \Rightarrow Fs=-E_{kin1} \Rightarrow F=\frac{-E_{kin1}}{s} \Rightarrow F=-\frac{mv^{2}}{2s}[/tex]

But that is all explained with examples in the links provided.

 

[rwisz]

I can definitely provide some help in determining the weight increase of a 12 stone occupant in a car crash at 30mph. The equation that can be used is the kinetic energy formula, which is KE = 1/2 * m * v^2. In this equation, KE stands for kinetic energy, m stands for mass, and v stands for velocity.

To calculate the weight increase, we need to first convert 12 stones to kilograms, which is approximately 76.2 kg. Then, we can plug in the values into the equation as follows:

KE = 1/2 * 76.2 kg * (30mph)^2

= 1/2 * 76.2 kg * (13.41 m/s)^2

= 1/2 * 76.2 kg * 180.2 m^2/s^2

= 6,886.86 Joules

This means that the kinetic energy of the 12 stone occupant at 30mph is 6,886.86 Joules. When the car comes to a dead stop, all of this kinetic energy is transferred to the occupant, resulting in a weight increase.

However, it is important to note that this equation only gives an estimate and does not take into account other factors such as the structure of the car, the type of crash, and the impact of airbags or other safety features. It is also important to remember that in real-life situations, the weight increase may vary due to factors such as the occupant's body composition and position in the car.

I hope this helps in your presentation on road traffic accidents. If you need more specific information, I would be happy to provide further assistance.