I am trying to work out horizontal ranges for a falling person from height (in 10m steps from 0m to 60m).

I have used this site http://www.convertalot.com/ballistic_trajectory_calculator.html to create a table of ranges and 'step off speeds' from Cross, R. (2008). Forensic Physics 101: Falls from a height. American Journal of Physics, 76(9), 833. http://doi.org/10.1119/1.2919736 covering speeds (Vo) from 0 m/s-1 to 4 m/s-1.

However, I am trying to work out if wind effects are going to be a credible factor with fall times of between 1.4 to 3.5 seconds.

Maximum resistance would be for a perfectly vertical person, worst case 2m x 0.5m in surface area. Again worst case would be wind effects the start of the drop to hitting ground zero.

Can someone help?


1 Answer 1


https://en.wikipedia.org/wiki/Drag_coefficient specifies the drag coefficient $c_d$ of an upright man as 1.0-1.3. With that you can calculate the drag force as $F_d=c_d\rho Av^2/2$. If we input the numbers we get $F=1.3*1.2kg/m^3*1m^2 * v^2/2=0.78N*(v/ms^-1)^2$. Even with a side wind of $10m/s$ this only amounts to a drag force of approx. $78N$. Assuming we have an 80kg body, the expected acceleration by the wind is on the order of $1m/s^2$, i.e. even for a fall time of $3.5s$ the sideways drift won't exceed $5m$ significantly and it will be considerably less for lower heights.

  • $\begingroup$ Thank you. I can add the additional horizontal velocity to the trajectory calculator to get the ranges from the drop point for different speeds. Just what I was looking for. $\endgroup$
    – GarethLock
    Commented Sep 9, 2015 at 16:06

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