Topic started by ray of hope (@ ppp-200-1-87.bng.vsnl.net.in) on Fri Oct 25 12:18:42 .
All times in EST +10:30 for IST.

Hello all!
I'd like to share my doubts,esp. in Physics,i wud be very grateful if any of u cud answer these,and share u'r doubts too here...
let's have fun with science :)
Well,to start off:
1)According to virial theorem,kinetic energy of a nody is half the potential energy,i.e,if
we take a satellite of mass m and velocity v revolving around a body of mass M,at a
distance R from it then,
GMm/2R=1/2mv^2.
Now,when the same theorem is applied to the sun,we say NkT=1/2GM^2/R,where N=avagadro
no.,k=boltzmann constanst,T=absolute temperature,M,R-mass and radius of the sun
respectively.My doubt is,how can the pressure of the gas inside the sun,i.e NkT be
considered as the kinetic energy of the sun?Shouldn't the K.E of the sun be the one by
virtue of it's motion?(just like 1/2mv^2 is the energy associated with the motion of the
satellite)
2)When we want to calculate the gravitational pressure at the centre of the sun,if we
consider 2 hemispheres of the sun,the force betn. them is given by,(GM/2*M/2)R^2.Where M
and R are the mass and radius of the sun respectively.How can the distance between the two
hemispheres be R?Or is that the distance between their centres og gravity?But even if it
is so,how do we know that the centre of gravity of the hemisphere will be at a depth
exactly 1/2 the radius?Could you also please explain the difference between centres of
mass and gravity?

Responses:

• From: stg (@ 12.151.162.48) on: Sat Oct 26 04:22:03
  
  I think the k.e is that of the gases inside the sun that is taken into accout. Since gases move I presume its that kinetic energy thats taken into calculation.
  
  
• From: Ray of hope (@ ppp-176-128.bng.vsnl.net.in) on: Sat Oct 26 09:35:19
  
  But my doubt was, if for the satellite it is 1/2mv^2,even for the sun,shudn't it be the energy due to revolution around the centre of the galaxy?Or whatever,but by virtue of its motion...
  
  
• From: ray of hope (@ ppp-176-97.bng.vsnl.net.in) on: Sun Oct 27 23:51:37
  
  someone pleease help
  :-(
  
  
• From: hans (@ ) on: Fri Mar 12 10:07:01
  
  i do not know where i can make an inquiry so i want my doubt to be cleared here.
  
  why i sit that our mouth stinks after every nap
  
  
• From: hans (@ ) on: Fri Mar 12 10:07:22
  
  i do not know where i can make an inquiry so i want my doubt to be cleared here.
  
  why is it that our mouth stinks after every nap
  
  
• From: pAraNOiD (@ 202.54.65.65) on: Fri Mar 12 10:50:55 EST 2004
  
  I think u r commiting a mistake some where..
  From what I see they are probably stating the reason why gases don't escape from the sun...
  
  and Nitish the answer is bacterias.
  I need to know more of your host masking technique.
  
  
  
  
• From: pAraNOiD (@ 202.54.65.65) on: Fri Mar 12 10:55:03 EST 2004
  
  Just visualize why we have a center to a circle ,
  sphere.. and the importance of equidistance from the center..i.e the radius.
  It is just the inverse square law being applied here..
  Inverse square laws are not confided to planets alone .. it is a mathematical concept ..learn about it.
  
  
• From: pAraNOiD (@ 203.199.222.217) on: Wed Mar 17 02:40:40 EST 2004
  
  Captain's blog star date .. as given above
  
  The given equation could also state something about the thrust generated by the satellite to compensate for Sun's gravitational pull.
  
  
  
• From: mallesh (@ ) on: Wed Sep 1 03:01:03
  
  why room get heated when refrigirator opened for long time
  
  
• From: Sarat (@ 61.11.79.222) on: Wed Sep 1 08:36:17 EDT 2004
  
  The refrigerater just knows to keep the temperature inside as what we instruct it to. when we open the refrigerator, the cool air escapes and to keep the temperature intact inside, the compressor needs to work extra which makes it more hot and that is radiated to the room rather than the cool air from the fridge.
  
  

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