23kk..
true or false.....with explaination
1) work done by kinetic friction on a body is never 0
2)work done by Kinetic friction on a system is always negative
plzzz give expalination also
-
UP 0 DOWN 0 0 20
20 Answers
21@qwerty so how can u say work done by Kf in tat case will be positive ....work done by KF also includes Work done by frictional torque which will be negative.....and wen u add both of them (i.e WD by frictional torque and linear workdone by kF) net work done will come out to be -ve
21well q is((( work done by Kinetic friction on a system is always negative)))....so we hav to take both workdone by frictional toque and wd by linear frictional force
if only asking abt wd by frictional torque then it is positive
23yeah ... but if we talk only about rotational work den ???
i mean ..if we want to conclude that whether KF can do +ve work or not ..then what shud be d correct statement ?
21but in this u cant actually say na ki net work done will be positive or negative
21no i wasnt talking abt this case which u hav shown in fig............in this workdone by frictional torque is +ve and workdone by linear frictional force in negative
23
eragon ..how is friction doing negative Rotational work in the above figure???
21nope work done by frictional torque is negative since it acts in the opposite direction to the direction of rotation of sphere and work done by linear frictional force is positive since it acts in the forward direction and net workdone by KF is sum of these two workdone and it comes out to be negative
so anwer will be true
23friction torque will do positive rotational work na ??
and ya agreed that total work done by the KF may be negative ...but if we consider individually , rotational work is positive , so KF can do +ve work .......[ the net work may be negative ...]
so wat shud be the answer of kaustab's question
19the first answer should be false because the work done by kinetic friction can be zero if we adjust our reference frame suitably !
the second answer is also false...kinetic friction does not always act in a direction opposite to the direction of motion of the body !
23xyz i said " if it isnt sufficient " i.e it cant support pure rolling"
rolling doesnt imply pure rolling.....
1no qwerty if it can support pure rolling
then how can friction be " kinetic'
23why?? what if a sphere is rolling down an inclined plane ...and if the friction isnt sufficient for pure rolling ..... then?
1kinetic friction doe snot do rotational work only static one odes
1for the second one....consider a two block system 1 kept over another...if one is applied with a force then on other kinetic friction does +ve work
23well kinetic friction can do +ve rotational work .........if we consider an example of a sphere rolling down an inclined plane.....
1answer for first is false and second is true....
anyways thanx for the first organic.....but second is true not false !!!!