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Blazing goIITian

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9 Jul 2009 22:50:24 IST

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Newton's 1st law states " EVERY BODY continues in its state of rest or of uniform motion in a straig

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Newton's 1st law states " EVERY BODY continues in its state of rest or of uniform motion in a straight line unless it is compelled by ext. force to change dat state. "suppose a time bomb is placed somewhere. It is at rest and we conclude dat it will continue to remain so. But after some time , the bomb explodes & da splinters run here and there. Obviously the body ( i,e da bomb or whatever remains of it ) can no longer said to be at rest as it was some time ago. And no EXTERNAL FORCE was put.

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BALGANESH

Blazing goIITian

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10 Jul 2009 10:50:20 IST

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well as far as i know the forces are internal only seconds before th ebomb explodes buut when it does explode the internal force acts as the external force for the pieces of the bombso its no longer internal froce as the bomb on the hwole does not existso he law isnt violatedexternal force is applied

djdylan2000. bits goa eee

Blazing goIITian

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10 Jul 2009 11:03:58 IST

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Well for one thing, Newtons law applies to only POINT masses.

When applied to extended bodies, it applies to its COM... and not strictly to any other part of the body...

~Áß???????

Blazing goIITian

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10 Jul 2009 11:07:20 IST

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SEE acc to me .

initially the system is at rest ..means the centre of mass of body (system _) is at rest .

now when the bomb explodes , even if the splinters are moving ..but the centre of mass of system is in rest only.

so when we say the body in rest ..we are referring to the centre of mass of body.

now u can`t say that ...as splinters are moving the state(inertia) of body is changed ..

here we have to concentrate on whole system and not on particles of system..

now ques...stayes why splinters move ..it is due to force acted due to mech energy ..which is

manifested by the internal chemical energy.

BEST OF LUCK

~Áß???????

Blazing goIITian

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10 Jul 2009 11:12:16 IST

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see RAMYANI..answer is already given by the .....users ..

and moderator too..!U ACCEPT THE ANSWER THAN ..NUGO WAS RIGHT..!

Vikram Saxena

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10 Jul 2009 11:17:32 IST

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initially the bomb is at rest(i.e. the momentum is zero)...and

Even after the explosion...

The COM of the bomb(materials) is still at rest....

The net momentum is zero.....

The int. energy is converted into K.E....

But the net momentum is still at rest...

Therefore the first law is not violeted..!!!

NugoRama

Blazing goIITian

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10 Jul 2009 11:34:42 IST

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Thanx ya all...

ramyani chakrabarty

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10 Jul 2009 14:41:54 IST

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Then should da 1st law be read as " The COM of everybody continues in its ..........."

Or should it be restated as da ppl of conservation of momentum ?

NugoRama

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10 Jul 2009 14:56:00 IST

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Its already stated to be valid for only point sized bodies...hence no need to use the word COM.

ramyani chakrabarty

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10 Jul 2009 23:21:41 IST

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is 1st law invalid for large body, sa, a cricket ball ?

ramyani chakrabarty

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10 Jul 2009 23:31:34 IST

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or shall we say newton's 1st law is invalid for a car. Let there be a car of mass 100 kg and a force of 200 N is applied on it. Can't we calculate the accln ?

So i don't think u r correct when u said " Its already stated to be valid for only point sized bodies "

NugoRama

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10 Jul 2009 23:32:56 IST

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No ..we cant calculate the accn of the car ..it has to be mentioned that the force is applied oon the COM...or we have to assume the same.

btw ..Hi !

NugoRama

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10 Jul 2009 23:33:54 IST

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While calculating forces on balls and other things ..it is assumed that forces are applied on the COM.

THERE IS NO LAW FOR LARGE BODIES.

ramyani chakrabarty

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10 Jul 2009 23:35:54 IST

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hi !

~Áß???????

Blazing goIITian

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11 Jul 2009 11:33:26 IST

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okk..okk....its over than..............NOW DO FURTHER INTRO IN ......NUDGEBOOK..

hahaha.........

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