Re: pinhole two questions

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From: pauld@exploratorium.edu
Date: Wed Oct 29 2003 - 18:00:57 PST 

Message-ID: <1398.209.239.173.234.1067479257.squirrel@www.exo.net>
Date: Wed, 29 Oct 2003 18:00:57 -0800 (PST)
Subject: Re: pinhole two questions
From: pauld@exploratorium.edu

Hi Mike

The students should note whether they feel hot or cold pockets of air or
hot places of enhanced radiation.
Walk near a wall that has been in the sun for a while and it will feel warm.

However hot air masses are possible.
Air near the ground warms and then rises as a "thermal" if you walk
through a thermal it will feel hotter.

Also if you are in a wind it feels cooler even if the air temp is the same
as a place where it is calm and feels hotter.

You are right! The accelerating object will either hit the planet or pass
by it and be slowed by the same gravity that sped it up. An orbit.

Paul D

> My students noticed that during the recent hot weather, they have
> felt hot and cold pockets of air as they walked around. We even went
> on a brief "hotspot" walk outside of our classroom and found a few.
> My only explanation was that the air pockets radiate from the ground
> as different surfaces create different temperatures, and that the
> breeze has been so light that it hasn't dispersed the air as normal.
> What did I miss?
>
> Another student asked whether an object moving in a gravitional field
> would accelerate indefinitely because there is no air resistance.
> He wanted to know if an object could reach super high speeds because
> of this. My answer: theoretically yes, but realistically no because
> the object would either hit the thing it was attracted to, or go into
> orbit around it, which would make it maintain a constant speed. Is
> this correct?
>
> Thanks for your help!
> Mike Schulist
> Miller Creek Middle School
>
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