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Is it necessary that work done in the motion of a body over a closed loop is 0 for every force in nature ? why ?
 one year ago
 one year ago
Is it necessary that work done in the motion of a body over a closed loop is 0 for every force in nature ? why ?
 one year ago
 one year ago

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akash123Best ResponseYou've already chosen the best response.2
no...it's not true for every force in nature
 one year ago

akash123Best ResponseYou've already chosen the best response.2
take the example of work done by friction force.
 one year ago

ashnaBest ResponseYou've already chosen the best response.0
can you first explain the question ? :)
 one year ago

akash123Best ResponseYou've already chosen the best response.2
dw:1348895881344:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
there are several forces in the nature..name them...whatever u know.
 one year ago

akash123Best ResponseYou've already chosen the best response.2
like electric force, magnetic force, spring force, friction force, gravitational force...
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akash123Best ResponseYou've already chosen the best response.2
dw:1348896083024:dw
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akash123Best ResponseYou've already chosen the best response.2
and these are all the closed loops
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ashnaBest ResponseYou've already chosen the best response.0
i have to keep refreshing OS as its goin down , so my replays may seem late n am sry for that ! okay understood.
 one year ago

akash123Best ResponseYou've already chosen the best response.2
dw:1348896151349:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
now suppose there is a ball situated at point A near the earth
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akash123Best ResponseYou've already chosen the best response.2
and the ball is taken from point A to B to C to D to A..that is ball has been moved on a closed loop during this motion
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akash123Best ResponseYou've already chosen the best response.2
dw:1348896421255:dw
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akash123Best ResponseYou've already chosen the best response.2
earth is exerting force mg on the ball...so tell me work done by this gravitational force if ball moves from point A to B...use work done= force* displacement * cos(theta)
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akash123Best ResponseYou've already chosen the best response.2
look for the angle between the force and the displacement
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akash123Best ResponseYou've already chosen the best response.2
yes..so work done by gravitational force( A to B)=0
 one year ago

akash123Best ResponseYou've already chosen the best response.2
our objective is the work done by the gravitational force on the ball so now we come to B to C
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akash123Best ResponseYou've already chosen the best response.2
dw:1348896858314:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
ball is moving from B to C again work done by the gravitational force = force*( displacement) *cos(theta) theta=?
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akash123Best ResponseYou've already chosen the best response.2
there are two vectors..force (mg, vertically downward) and displacement( B to C)..so think carefully for angle between them.
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akash123Best ResponseYou've already chosen the best response.2
displacement ( B to C) is vertically upward.
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akash123Best ResponseYou've already chosen the best response.2
dw:1348897246563:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
dw:1348897411835:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
does it make sense for visualizing the angle between two vectors pictorially?
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akash123Best ResponseYou've already chosen the best response.2
so now we come to B to Cdw:1348897603389:dw
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akash123Best ResponseYou've already chosen the best response.2
force is vertically downward and displacement is vertically upward so angle between them is......?
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akash123Best ResponseYou've already chosen the best response.2
yes...right..:) so work done by the gravitational force = force*( displacement) *cos(theta) = mg * h * (1) =mgh suppose BC=h
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akash123Best ResponseYou've already chosen the best response.2
till now...it's fine?
 one year ago

akash123Best ResponseYou've already chosen the best response.2
now work done by gravitational force (C to D)= 0 does it make sense?
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akash123Best ResponseYou've already chosen the best response.2
dw:1348898023808:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
now we come to work done by the gravitational force on the ball (D to A) tell me how much it'll be?
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akash123Best ResponseYou've already chosen the best response.2
just look for angle between gravitational force and displacement when ball moves from D to A
 one year ago

akash123Best ResponseYou've already chosen the best response.2
so work done by the gravitational force on the ball (D to A)= mg* h* cos(0)= mgh BC=DA=h
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akash123Best ResponseYou've already chosen the best response.2
so our objective has been completed...I mean...we have calculated...work done by gravitational force on the ball when the ball moved on a closed loop.
 one year ago

akash123Best ResponseYou've already chosen the best response.2
so total work done= W(A>B) + W(B>c) + W(C>D) + W(D>A) =0 + (mgh) + 0 + mgh =0
 one year ago

akash123Best ResponseYou've already chosen the best response.2
so work done by gravitational force in the motion of a body over a closed loop is 0.
 one year ago

ashnaBest ResponseYou've already chosen the best response.0
okay understood , and why is this not the same for every force in nature ?
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akash123Best ResponseYou've already chosen the best response.2
but we took a rectangular loop for a closed loop..one can show this for any arbitrarydw:1348898826574:dw closed loop
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akash123Best ResponseYou've already chosen the best response.2
but it's not true for every force in nature...e.g. friction force
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akash123Best ResponseYou've already chosen the best response.2
so we classify the forces into two type if work done by the force over a closed loop is zero then conservative force otherwise nonconservative force
 one year ago

ashnaBest ResponseYou've already chosen the best response.0
i don't understand , why not for frictional force ?
 one year ago

akash123Best ResponseYou've already chosen the best response.2
yes...I am coming there
 one year ago

akash123Best ResponseYou've already chosen the best response.2
1st have a look...why not zero?dw:1348899134273:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
suppose there is a block of mass m moves on a rectangular loop, and the loop is kept horizontally on the earth
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akash123Best ResponseYou've already chosen the best response.2
dw:1348899311394:dw
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akash123Best ResponseYou've already chosen the best response.2
do u agree that work done by the friction force on the block will be negative in each segment(AB, BC,CD,DA) of this loop?
 one year ago

akash123Best ResponseYou've already chosen the best response.2
because during motion, angle between friction force and displacement will be 180'
 one year ago

ashnaBest ResponseYou've already chosen the best response.0
am sorry but i did not understand the last part !
 one year ago

akash123Best ResponseYou've already chosen the best response.2
which one...do u agree that work done by the friction force on the block will be negative in each segment(AB, BC,CD,DA) of this loop?
 one year ago

akash123Best ResponseYou've already chosen the best response.2
ok...1st we'll see the work done by the friction force on the block,when it moves from A to B again work done= force*( displacement)* cos(theta) theta=?
 one year ago

akash123Best ResponseYou've already chosen the best response.2
dw:1348899953137:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
dw:1348900005470:dw
 one year ago

akash123Best ResponseYou've already chosen the best response.2
see..if block moves from A to B then displacement of block =AB...right?
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akash123Best ResponseYou've already chosen the best response.2
direction of displacement is to the right and the direction of friction force is to the left
 one year ago

akash123Best ResponseYou've already chosen the best response.2
so again there are two vectors friction force and displacement...look for the angle between them carfully
 one year ago

sam291Best ResponseYou've already chosen the best response.1
But when it moves from C to D the direction of the force vector is opposite from the direction from A to B, so it will still add up to zero going around the loop. Am I wrong?
 one year ago

kappa007Best ResponseYou've already chosen the best response.1
Forces in nature can be either conservative or nonconservative. Work done in a closed loop by a conservative force is always 0 .
 one year ago
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