# Hydrodynamic force of water droplet stated in psi at various mpg

1. May 4, 2013

### weathergage

I'm not a student of physics but do have puzzle I am trying to solve. Is there a way to calculate the force of a water droplet impacting a vertical surface stated in psi at various speeds of impact? A more practical way to state the problem would be; what psi will rain impact the chest of a motorcycle rider(sitting tall without a fairing) at 20mph, 40mph, 60mph etc?

The second part of the question is would the psi result change depending on the density (number of water droplets per square inch) of the water? Light rain vs. heavy rain, vs. riding that motorcycle into the vertical surface of a tidal wave?

Thanks in advance for any help. Best Regards, Washley

2. May 4, 2013

### Naty1

Can't answer the question but someone likely has taken measurements.....
Because water deforms as it hits a solisd surface, the FT =mv relationship is not an obvious one.

The force of wind alone varies as the square of velocity.....and I can tell you from boating
experience water hitting you face at about 40 mph stings and without protective eye wear
you can barely see....at around 60 mph....it hurts a lot and you cannot see.

edit: no answers but cool pictures here:

http://en.wikipedia.org/wiki/Drop_(liquid [Broken])

Last edited by a moderator: May 6, 2017