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17 Jul 2007 17:09:53 IST
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I am facing difficulties regarding using of sign conventions in kinematic problems especially motion under gravity .
Plz give me some tips.
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17 Jul 2007 18:26:46 IST
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where can i get some iit material on the net for free
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"I don't know What i may appear to the world, but to my self, i seem to have been only like a boy playing on the sea shore and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary wile the great ocean of truth lay all undiscovered before me" - Sir Issac Newton |
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17 Jul 2007 18:30:13 IST
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The upward displacement is generally taken as positive and the downward displacement is taken as negative. while moving up, g is taken as negative and vice versa.For a body moving along a st. line with decreasing velocity or stopping, acc. is taken as negative and vice versa. pl rate me if you are convinced.
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"I don't know What i may appear to the world, but to my self, i seem to have been only like a boy playing on the sea shore and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary wile the great ocean of truth lay all undiscovered before me" - Sir Issac Newton |
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17 Jul 2007 18:31:46 IST
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There are many sign conventions. Stick to one and use it.
I use the following for problems of particles in gravitational field.
Take the Y axis positive up and origin wherever you like.
Consider a particle released from rest from a height H.
Suppose the origin is at the initial position of the particle, then for the motion from top to bottom,
Initial velocity, v0 = 0
Initial position, y0 = 0
Final position, y = -H
Acceleration, a = -g
Final velocity, v
v2 = v02 + 2a(y-y0) = 0 + 2(-g)(-H-0) = 2gH
v = - 2gH
We take the negative root as the velocity is directed down.
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22 Jul 2007 23:18:38 IST
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if we done any work opoosite to gravity then it will be negative whether it is acceration velocity or any other if body come close due to force of attraction then it wiil be negative
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24 Jul 2007 18:18:26 IST
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am Thankfull to all...
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