1bhaiyya if he is inside the train he is not doing work and if he is outside itzzz certainly -ve work...bhaiyya..........
A man pushes a compartment of a train in the direction in which the train is accelerating uniformly. Will the man do +ve ,-ve or no work ?
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62yes abhishek you are right in your analysis..
on the whole there is no work..
But if you have to find the work on the train by the man it is -ve.
while the wrok by the train on th eman will be +ve.
This is in someway the netwon's law.. "every action has equal and oppsoite reaction"
1yes bhaiyya plz check this statement
the work (-ive ) done in this case will be equal to the work that the man was doing on the train anytime he was standing still..(wrt train ofcourse)
if this is correct i'll ask two more..
1no not that ...
i mean while pushing the wall the man applies some force on the wall
due to which there is positive work....
and then there is the force his feet aply in the backward direction ..
which is (i think > than the force of his hands) so net work -ive ???
i know there is something messy in this so please tell me where am i wrong ...
62he is on the train..
his net acceleration is forward. (equal to train's)
So the net force.. friction (ground) - reaction will be in forward direction.
So work done by the train on him wil be +ve.
___ (more added below)
So the work done by the person on the train will be -ve
1sorry for troubling u but
Q1)
yes so there should be no change in the wrok done by the train on him (wil be +ve.) regardless of whether he is pushing or pulling the wall or doing yoga..
(unless he jumps)
oops yes so Q2
Q2) will work change in case man starts walking...
62Philip: The question is work by man on train.. :!!!!
So that has to be -ve
your statement 1 is correct.
2) Walking will not change the work/ force unless he is accelerating
1nishant ,abhirup or anyone else i can't undestand why work is -ve.
1hmmm... nice one ...
so when we walk with uniform speed no work is done...
walking is ambiguous bhaiyya don't u think
i mean it will be much better if we restrain ourselves to simple objects that maintain constant contact with the ground
thanks i think my doubt is cleared..
lolzz just imagine a man walking with uniform velocity v
and suddenly he enters a frictionless floor
he is supposed to keep on walking like that lol [9]
1if a box is inside an accelerating train and a man is pushing the box in the same direction of that of the train.
will the work done by the man be same with respect to a fellow traveller and by a stationary observer standing outside the train??
1suppose if someone(not me) inside the train bangs himself to the compartment
and bounces back.....then what will the work done by the person on the train...
if net displacement during this is negative....
62mkagenius it depends on a lot of things...
It depends on how long in that whole process he was in contact with the train and in what way.
It is not a very easy one to answer...
On the whole you could say that if there was no contact except during the time of collision, then
work done will be F.ds.. force during collision by the man on the tain will be in the forward direction. Train is also moving in forward direction.
So the work by man on the train wud have been positive!
11bhaiya i suppose 0 work as, as due to push of the man, there is no net displacement.
62no eureka.. you dont have to find the work by the system.
You have to find the work done by the man of the train.
SO you cant take these together as a system.
24ok..........i will give it another try....
but was that statement true.....Internal force dont perform net work on the system ????????
1i think heell do negative work.........
and W=-Fat2/2
as if we bring the man in the compartement to an inertial frame ...a pseudo force will be applied on him in the opposite dir and that will be the direction of displacement...
62Check the image i have attached. (F is the frictional force. R is the normal reaction)
Work done by the man will be R.s-F.s
but we know that F-R=ma because the train is accelerating forward with the same acceleration as the man.
So F-R is positive.
So the man will do -ve work.
62This is a question I got from Aniruddha today.
An extremely good one.. Some one pls try to solve this.
9its -ve if the man is inside the train
+ve if hes outside
Q dint mention abt that