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Mechanics

Blazing goIITian

 Joined: 16 Mar 2007 Post: 838
5 May 2007 11:30:36 IST
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Engineering Entrance , Medical Entrance , AIPMT , JEE Main , AIIMS , JEE Advanced , Physics , Mechanics

Hey guys and gals check this out!!!!!!!!
A sphere of mass m and radius  r is  projected  in a viscous medium of coefficient of viscosity n (eta) with a speed v.Find the distance travelled and time taken before it stops when it is projected in :-
i)gravity free space;
ii)presence of gravity

Cool goIITian

Joined: 22 Apr 2007
Posts: 91
5 May 2007 13:14:59 IST
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in gravity free space it is 0

New kid on the Block

Joined: 19 Apr 2007
Posts: 25
5 May 2007 18:05:26 IST
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how it is zero ?

Blazing goIITian

Joined: 16 Mar 2007
Posts: 838
5 May 2007 18:48:34 IST
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Well answer for the first part is not 0.

Hot goIITian

Joined: 17 Mar 2007
Posts: 104
5 May 2007 19:24:04 IST
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in gravity free space it will travel infinitely after attainin terminal velocity......am i right?

Hot goIITian

Joined: 17 Mar 2007
Posts: 104
5 May 2007 20:02:54 IST
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no yaar sorry,......thts wrong

Blazing goIITian

Joined: 16 Mar 2007
Posts: 838
10 May 2007 21:04:37 IST
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Hey anyone???????????????????????I myself don't know the answer
and I have to get the answer as I have a test on entire mechanics this coming tuesday.

New kid on the Block

Joined: 11 May 2007
Posts: 1
11 May 2007 12:01:48 IST
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IN G FORCE:-
THE SPEED=THE FORCE ACTED ON BODY.* G CONT
& THE TIME= F* DISTANCE[S]*G CONT

ALSO THE METOD OF ANS. IS IS SAME FOR THE SEC. ONE BUT THE ANS HAS TO BE DIV.BY G CONT.

Blazing goIITian

Joined: 3 Feb 2007
Posts: 1200
11 May 2007 13:22:14 IST
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hey if there is no gravity at all then there is no questio of any bouyancy or any other force so only viscous force comes into play here..........

Therefore we have a retarding backward viscous force say F, acting on the sphere, which is
F=6rv
also      F=ma,             here 'a' is the retardation due to viscous force.
on comparison we have.....

ma = 6rv   --------------------(1)

but from the equation of motion "V=U+at" we have V=0, U=v and  a = -a

therefore U=at=v   ------------------ (2)

from (1) and (2)

t = m / (6rv)

similarly we can calculate for distance...........

I hope my approach is right if yes then pls rate me Thanks........

Cheers....................

Blazing goIITian

Joined: 3 Feb 2007
Posts: 1200
12 May 2007 17:55:41 IST
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knock knock!!!!!!!!!!

someone there??????????/

Blazing goIITian

Joined: 16 Mar 2007
Posts: 838
12 May 2007 20:54:02 IST
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YA AATISH actually I was verifying your answer and I found that you are correct.Thankx.But yaar please try to find out the answer for part (ii) also i.e. time and distance in presence of gravity.

Blazing goIITian

Joined: 3 Feb 2007
Posts: 1200
13 May 2007 14:23:21 IST
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Hey buddy I tried for it but could not succeed.........

I think we must ask this one to experts.........

Cheers...........

Cool goIITian

Joined: 28 Apr 2007
Posts: 81
14 May 2007 19:41:29 IST
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hi guys you have forgotten the fact that viscosity is proportional to instantaneous velocity...
use calculus n you will get the answer....
as far as second question is concerned...as the solid will fall with terminal velcoity.........so it will travel infinitely...

Blazing goIITian

Joined: 16 Mar 2007
Posts: 838
14 May 2007 21:51:45 IST
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We know that pcdagr.But still , using calculus we are not getting a perfect final answer.If you think you can do it then please post the final

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