Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
ashna
Group Title
Is it necessary that work done in the motion of a body over a closed loop is 0 for every force in nature ? why ?
 2 years ago
 2 years ago
ashna Group Title
Is it necessary that work done in the motion of a body over a closed loop is 0 for every force in nature ? why ?
 2 years ago
 2 years ago

This Question is Closed

akash123 Group TitleBest ResponseYou've already chosen the best response.2
no...it's not true for every force in nature
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
take the example of work done by friction force.
 2 years ago

ashna Group TitleBest ResponseYou've already chosen the best response.0
can you first explain the question ? :)
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348895881344:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
there are several forces in the nature..name them...whatever u know.
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
like electric force, magnetic force, spring force, friction force, gravitational force...
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348896083024:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
and these are all the closed loops
 2 years ago

ashna Group TitleBest 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.
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348896151349:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
now suppose there is a ball situated at point A near the earth
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348896421255:dw
 2 years ago

akash123 Group TitleBest 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)
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
look for the angle between the force and the displacement
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
yes..so work done by gravitational force( A to B)=0
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348896858314:dw
 2 years ago

akash123 Group TitleBest 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=?
 2 years ago

akash123 Group TitleBest 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.
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
displacement ( B to C) is vertically upward.
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348897246563:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348897411835:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
does it make sense for visualizing the angle between two vectors pictorially?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
so now we come to B to Cdw:1348897603389:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
force is vertically downward and displacement is vertically upward so angle between them is......?
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
till now...it's fine?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
now work done by gravitational force (C to D)= 0 does it make sense?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348898023808:dw
 2 years ago

akash123 Group TitleBest 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?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
just look for angle between gravitational force and displacement when ball moves from D to A
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest 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.
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest 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.
 2 years ago

ashna Group TitleBest ResponseYou've already chosen the best response.0
okay understood , and why is this not the same for every force in nature ?
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
but it's not true for every force in nature...e.g. friction force
 2 years ago

akash123 Group TitleBest 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
 2 years ago

ashna Group TitleBest ResponseYou've already chosen the best response.0
i don't understand , why not for frictional force ?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
yes...I am coming there
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
1st have a look...why not zero?dw:1348899134273:dw
 2 years ago

akash123 Group TitleBest 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
 2 years ago

ashna Group TitleBest ResponseYou've already chosen the best response.0
like before , okay !
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348899311394:dw
 2 years ago

akash123 Group TitleBest 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?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
because during motion, angle between friction force and displacement will be 180'
 2 years ago

ashna Group TitleBest ResponseYou've already chosen the best response.0
am sorry but i did not understand the last part !
 2 years ago

akash123 Group TitleBest 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?
 2 years ago

akash123 Group TitleBest 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=?
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348899953137:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
dw:1348900005470:dw
 2 years ago

akash123 Group TitleBest ResponseYou've already chosen the best response.2
see..if block moves from A to B then displacement of block =AB...right?
 2 years ago

akash123 Group TitleBest 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
 2 years ago

akash123 Group TitleBest 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
 2 years ago

sam291 Group TitleBest 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?
 2 years ago

kappa007 Group TitleBest 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 .
 2 years ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.