33@abhishek
lugaage ko push bhi to kar sakte hain... jaroori thode hi hai ki sir par hai...
A: If a porter carries a luggage of 30 kg from the waiting room of a
railway station to the platform and bring it back to the waiting foom
the work done by him is zero
R: Workdone is defined as the scalar product of force applied and the
displacement vector which in this case is zero..
I thot the answer to b A...but answer is A is wrong R is true..
cud someone explain
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6 Answers
1sriraghav
under ideal conditions, the work done in each inteval of time is zero as the force is perpendicularly up while the porter moves in horizontal direction...so i don't see any reason that a is false
33W=∫F.ds
F.ds is always positive.. its integral is never zero unless F=0
What is done is that..
W=F.∫ds=0 as ∫ds=0
But what is wrong in above statement is that... F is not constant for whole so can't be taken out...
so correct one would be...
W=w∫rFs + r∫w(-F)(-ds) ... which is non zero
that -F is not taken care of in wrong statement.
w∫r means from waiting room to railway platform
33
62actually even sir pe rakhne se it wont work
the potter has to apply horizontal force. If he doesnt how will the luggage move?
There is a smalll issue though..
if the acceleration fo the potter is zero.. then work done will be zero.!!!
So the question is ambiguous in a way!
1soory bhaiya actually 9th class ka NCERT se yahi exxample diya jata tha 0 work done ka so i got biased[1]
62yup.. somehow they do that..
it is work done by gravity which is zero..
wok done by normal reaction which is also zero...