warm and cold winds

[Bryden, Francis]

Hi David

 

The way I think of it is..........

 

The temperature of the air (and the thermal energy your skin loses to it
) depends on the kinetic energy of the randomly moving particles.

 

In warm air the particles have greater KE and so the skin loses less
thermal energy because there is a smaller temperature gradient.

 

I suspect the KE of the airparticles due to the wind is small compared
with the KE due to their normal random motion. 

 

(Wind has no effect on the temperature of a thermometer. Point a fan at
a thermometer and the effect is negligible.)

 

 Wind has two effects on us.

 

 We are usually warmer than the air, and there is a layer of warm air
near our skin that we have heated up, this will keep us warm. Any wind
will move this warm layer away.

 

Because we sweat, wind will also cool us as it increases the rate of
evaporation, taking thermal energy from our skin

 

 

 

Thanks ................ Francis

 

Francis Bryden

HoD Physics

St Cuthbert's College

122 Market Rd               or Box 26 020

Epsom                              Epsom

Auckland 1051                   Auckland 1344

New Zealand                      New Zealand

 

ph: 63 9 5204159 ext 7808

 

fbryden at stcuthberts.school.nz <mailto:fbryden at stcuthberts.school.nz> 

-----Original Message-----
From: phys-teach-talk-bounces at nzip.org.nz
[mailto:phys-teach-talk-bounces at nzip.org.nz] On Behalf Of David Housden
Sent: Friday, 9 May 2008 6:59 a.m.
To: phys-teach-talk at nzip.org.nz
Subject: FW: warm and cold winds

 

Hi all

I'm not sure this actually got sent to everyone so I will resend on
David King's behalf.

Cheers

David Housden

 

From: phys-teach-talk-bounces at nzip.org.nz
[mailto:phys-teach-talk-bounces at nzip.org.nz] On Behalf Of David King
Sent: Thursday, 8 May 2008 11:01 p.m.
To: PHYSICS TALK
Subject: warm and cold winds

 

Can someone help?

 

I got myself in a bit of a confuddle yesterday trying to answer a pupils
question.

 

"Sir, why, if temperature is to do with Kinetic Energy is wind cold?"

 

I started on evaporation from the skin etc and the idea of us 'feeling'
cold, when he asked

 

"Why do we have warm winds? What's the difference?"

 

I started to answer then stopped. What makes air particles travelling at
whatever kph warm or cold?

 

Cheers

 

 

David King

Physics HoD

Christ's College

Private Bag 4900

Christchurch

New Zealand

 

 

 

 

 

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