State that WORK is DONE or NOT.....
A Wind-Mill is lifting water from a well.
and also justify your answer..

- mayankdevnani

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- mayankdevnani

am confusing.....plz help me

- anonymous

for windmill work is not done and for water work is done!

- mayankdevnani

no @VV-EFF question is one!!

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## More answers

- mayankdevnani

@sirm3d

- anonymous

work is done then! because windmill is applying force to pull up the water and the water itself displaces! now it depends on the angle between the force applied by the mill and the direction of water!

- mayankdevnani

yaa.. i know but my teacher says the work done is zero..

- anonymous

she would be considering cosQ =0, then she's right

- mayankdevnani

can you help me @ganeshie8 and @gerryliyana

- mayankdevnani

what is this? i can't understand

- anonymous

workdone=FxDxcos(Q) where Q is the angle between the force F and displacement D.

- anonymous

the work done is zero., because windmills always return to the original point

- mayankdevnani

how can we know that angle is of cosQ

- anonymous

yeah thats the point @gerryliyana ! he is considering water anf mill, both as a system!

- anonymous

and in case of water ! water is displaced by force!

- mayankdevnani

work is done then! because windmill is applying force to pull up the water and the water itself displaces! now it depends on the angle between the force applied by the mill and the direction of water!
@gerryliyana in this case!!

- anonymous

nice @VV-EFF

- mayankdevnani

so in that case...

- anonymous

nice What! @gerryliyana ! gve him the answer man! lol....

- mayankdevnani

so finally whats the conclusion of this answer.

- mayankdevnani

@Aperogalics have a look!!

- anonymous

the conclusion is that if u are considering the both as a system then the work is done ; iff Q is not equals to 1.5707. and if the system is only the mill then the work is said to be not done!!

- mayankdevnani

but the answer is to be written is one

- anonymous

work is not done! then

- mayankdevnani

in my solution book answer is work is done and the reason is that windmill pulls the water against the gravity...

- anonymous

@mayankdevnani there are two thing work done by the system and work done on the system here if the system is windmill then work done by the system is zero as there is no net dispacement while work done by the system is +ve as he make the water to be displaced........:)

- anonymous

obviously !!!!! @mayankdevnani if its against the gravity the according to the equation F=ma , water has mass and the acceleration is .9.8 mLsecsquare! then the force definitely exists ! and so the workdone!

- mayankdevnani

so what's the answer??

- anonymous

now dude stop confusing your self! the answer is that the work is certainly done by the system!

- mayankdevnani

m really confused @Aperogalics and @VV-EFF what is the concluded answer and answer should be one means both work done or not

- mayankdevnani

so i am correct and my teacher is wrong!!!

- anonymous

yeah!

- anonymous

work is done by the system! its certain!

- mayankdevnani

sure...are you sure about this!!

- anonymous

yeah!

- mayankdevnani

let @Aperogalics be write and then think,. he has creative mind...let @Aperogalics be answer

- anonymous

@mayankdevnani @VV-EFF is very clever he is still saying work is done by the system if ur mam is talking about work done on the system then she is correct and if not then you are correct.........:)

- mayankdevnani

no my mam says that the work be zero and i say that work is not zero @Aperogalics

- anonymous

lol.. what an answer @Aperogalics

- anonymous

@mayankdevnani yes ur mam says work is zero but is it by the system or on the system???????????
do you know about which she was talking about??????????????

- mayankdevnani

no.. my friend george said that mam says the work done is zero

- mayankdevnani

and also 1 thing

- mayankdevnani

my senior friend also says that _____
"lifting water" is the work that is done. When anything is lifted - it is moved (displaced) upward against the force of gravity. The force that lifts the object (water) must be greater that that of gravity or the object won't displace upward. The Net force that acts upward to lift (object, water, etc) multiplied by the vertical lift height is defined to be the work done in this process.

- mayankdevnani

secondly, there are not more than one work done... right..

- mayankdevnani

lastly , what's the concluded answer suppose you are in examination hall and you have a pen and this question ...how would you solve it?
@Aperogalics and @VV-EFF

- anonymous

i would say that u plz read the conversation above! and conclude the answer urslf!

- anonymous

@mayankdevnani answer my question and you will get the answer by yourself:)

- mayankdevnani

plz

- anonymous

a basic question in every book
suppose a man lifts a box to his head and walk 40kms .
IS THE WORK DONE BY THE PERSON?

- mayankdevnani

no work done is zero

- anonymous

why????????

- anonymous

@mayankdevnani

- mayankdevnani

because force acts in perpendicular direction\[90^{0}\] and displacement is at right angle

- mayankdevnani

right @Aperogalics

- anonymous

is the work is done against gravity?????

- mayankdevnani

|dw:1352199535611:dw|

- mayankdevnani

no @Aperogalics

- anonymous

why?????

- mayankdevnani

why thats have no answer

- anonymous

yes that's the thing force is applied against gravity and displacement is zero here|dw:1352199714164:dw|
there displacement is in perpendicular direction and here no displacement

- anonymous

getting it???????

- anonymous

@mayankdevnani

- mayankdevnani

thnx... i get it

- anonymous

always for you help
here i asked 2 different question bith r work but done by different systems.....k:)
so if the question is of IIT then it will mention the system otherwise my first post is the answer:)

- anonymous

I will say a small thing that "pulley" is the main thing here... |dw:1352284103729:dw|

- anonymous

nice @SheldonEinstein

- anonymous

THanks @gerryliyana :)

- mayankdevnani

@SheldonEinstein so that the work done is zeroo..you would say that

- anonymous

I had said that and yes Work done is ZERO! (if we are talking about a diff. kind of system)

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