Re: [Phys-l] Good Questions

["Jim Krider" <James.Krider@asu.edu>]

Hewitt has an overhead with this question on it.
Heat flow is proportional to delta T.  If you wait to put the cream in
your coffee delta T is large for ten minutes allowing a fast flow of
heat.  If you put the cream in right away delta T becomes smaller and
the amount of heat flow is much less for ten minutes.

 

Jim Krider Laboratory Coordinator Senior

PIRT - Physics Instructional Resource Team

Arizona State University

P.O. Box 8751504 Tempe, AZ 85287-1504

480-727-8391 FAX 480-965-7954 james.krider@asu.edu

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Bernard
Cleyet
Sent: Tuesday, October 10, 2006 10:25 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Good Questions

#3 is the only question I remember from intro Physics in 1955.  It was 
not in the text, but part of a lecture.  It was a question going the 
rounds in the U of Calif. system.

Has anyone done this experiment.  I was suspicious as the appropriate 
emissivity is not in the visible.   Can this cancel the other obvious 
reason to wait?

Note this experiment:

http://www.madsci.org/posts/archives/2000-09/969405728.Ph.q.html

and:

http://www.madsci.org/posts/archives/2000-09/969405728.Ph.r.html


bc



Jeffrey Schnick wrote:

> 1) Suppose you fire a bullet from a gun, and then, using the same
amount
> of gunpowder, you fire a blank from the same gun. In which case is the
> recoil greater?
>
> 2) (A former member of the College karate club asked me a question that
> has resulted in my asking this one in class.) In a karate
demonstration,
> you see a person break a stout board with her bare hand. While her hand
> is in contact with the board, how does the force of her hand on the
> board compare with the force of the board on her hand?
>
> 3) (I saw one like this, many years ago in an old thermodynamics
> textbook.)  You have a mug of coffee but your coffee is too hot. You
> want to start drinking it in three minutes. You drink your coffee with
> cream. You have just the right amount of cold cream to make the
beverage
> have just the right flavor. It takes you 5 seconds to mix in the cream.
> In which case would your beverage be cooler in three minutes: Wait 2
> minutes 55 seconds and then mix in the cream; or; mix in the cream
right
> away and then wait 2 minutes 55 seconds.
>
> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu
> [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Cliff
> Parker
> Sent: Saturday, October 07, 2006 6:26 PM
> To: Forum for Physics Educators
> Subject: [Phys-l] Good Questions
>
>  
>
> > I am looking for good questions...
> >    
> _______________________________________________
> Forum for Physics Educators
> Phys-l@carnot.physics.buffalo.edu
> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
>
>
>  
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l