# Calculate speed at which two groups move towards each other

**URL:** <https://gromacs.bioexcel.eu/t/calculate-speed-at-which-two-groups-move-towards-each-other/3720>\
**Category:** User discussions\
**Created:** [February 22, 2022, 12:27am UTC](https://gromacs.bioexcel.eu/t/calculate-speed-at-which-two-groups-move-towards-each-other/3720 "2022-02-22T00:27:24Z")\
**Posts on this page:** 1\
**Showing post:** 4

<div class="post-metadata">

**Author:** ![Marius](https://avatars.discourse-cdn.com/v4/letter/m/ed655f/32.png) [@Marius](https://gromacs.bioexcel.eu/u/Marius)\
**Post date:** [February 23, 2022, 7:17am UTC](https://gromacs.bioexcel.eu/t/calculate-speed-at-which-two-groups-move-towards-each-other/3720/4 "2022-02-23T07:17:02Z")

</div>

Hi @kwaldner,

please take a look at this recent blog post:

> [@How to get the velocity of the COM of a pulling group?](https://gromacs.bioexcel.eu/t/how-to-get-the-velocity-of-the-com-of-a-pulling-group/3693):
>
> GROMACS version: 2018.8 Hello, I am using the COM pulling options in my .mdp file. The distance of the COM of a group is outputted by default. But at the same time, I also want to get the velocity of the pulling groups. I could use the results of the distance of the COM to calculate the velocity by \Delta D/ \Delta t, but the problem is that the fluctuation is extremely high and the data becomes useless. Although some data smooth methods can be used to reduce the fluctuation, the result is sti…

Cheers,  
Marius

---

_[View the full topic](https://gromacs.bioexcel.eu/t/calculate-speed-at-which-two-groups-move-towards-each-other/3720)._