# Homework Help: Wind speed acting on a moving vehicle

1. Apr 24, 2014

### woodsy483

Hi all, newby here that could do with a little help.

I'm doing a college project and need to work out the head wind speed in m/s that a vehicle would encounter at a various range of speeds in mph, for example a high speed train, so I can compile a graph of the data ranging from 10mph up to 125mph.

2. Apr 24, 2014

### SteamKing

Staff Emeritus
It's a little unclear what you are asking: are you looking for a conversion of speeds from units of miles per hour to meters per second, or something else?

1 hour = 3600 seconds
1 mile = 5280 feet
1 meter = 3.2808 feet

3. Apr 24, 2014

### Rellek

http://en.wikipedia.org/wiki/Drag_(physics [Broken])

Not really sure what you're asking for here!

Last edited by a moderator: May 6, 2017
4. Apr 25, 2014

### woodsy483

basically I need to know is there an equation I could use to determine the speed of the wind hitting the front of a train if the train is travelling at 10mph,15mph,20mph and so on up to 125mph.

Another way of looking at it would be, if I fitted an anemometer on top of a train how fast would it spin if the train was hurtling along the track

5. Apr 25, 2014

### SteamKing

Staff Emeritus
Well, the wind speed the train (or any moving object) sees depends on the speed of the vehicle and the speed of the wind and the direction of the wind relative to the vehicle. This is covered in a basic dynamics course.

For example, if wind with a speed of 10 mph is blowing directly into the front of a car traveling 60 mph, from the standpoint of the car, it is as if the car were standing still and a 70 mph wind were blowing from the front. If, on the other hand, this same 10 mph wind is blowing from the rear of the car, then from the standpoint of the car, it is as if a tail wind of 50 mph is blowing from the rear as the car is standing still. For oblique angles, the wind velocity and the car's velocity are both vector quantities, so each can be decomposed into components and combined vectorially.

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