Question

A disc has pure rotation.It has angular velocity w.It then comes into contact with a surface which has static friction us,kinetic friction uk and rolling friction ur,When will the disc stop?

Answer 1

@RnR @Mashy

Answer 2

Dude ye aasan hai. Maine dad se samajhna tha aaj.

Answer 3

:/ please pass the knowledge :P

Answer 4

[Whenever u have time]

Answer 5

Sure. :P nhi to mashy to hai hi. :P

Answer 6

:}

Answer 7

uske bina kya hoga hamara?!?

Answer 8

Mai aaj maths kuch nhi padha. :'(

Answer 9

lol..sorry :(

Answer 10

maine bhi nahi pada :D kal se..co-ordinate ati h?

Answer 11

Haan aati hai maine bhi pdhni thi aaj. abhi pdhunga. complex kal khatam krunga.

Answer 12

ye question kab bataega?kal batadio..abhi padle..

Answer 13

Ok. Do minute soch rha hun bas.

Answer 14

itni jaldi bhool gaya? O_O

Answer 15

Kya?

Answer 16

kya soch rha hai?

Answer 17

lets talk in english :|

Answer 18

Ye sum. Matlab kal papa pehle merese puchenge kaise kiya tune. :P

Answer 19

Chal chad. mai chala. bye.

Answer 20

oh "samajhna" tha :| i thought samjha tha LOL sorry tabhi i wrote forgot..

Answer 21

First the disc will slip, so kinetic friction will be at work. Then its slipping velocity will become zero and rolling friction will act until it stops.

Answer 22

I had a question,like whenever a disc or a body rolls will it always aim towards achieving pure rolling?friction will always act in such a way to make it pure roll?if its in pure-translatory/rotatory motion if we say intially..does that decrease the system's potential energy ?so its favoured ? if you get my question :| for example here,right now it just has pure rotation,and friction will definitely act to make it pure roll and rolling friction is 1/100th of slipping one right? wouldnt make much difference?But its about PE of system and such..

Answer 23

#Foreverconfusedinphysics

Answer 24

If anything happens on its own I assume it reduces PE of the system D:

Answer 25

I think I heard somewhere that Work done by friction is 0 in pure rolling so that's neutral PE,not sure

Answer 26

Q1 :"I had a question,like whenever a disc or a body rolls will it always aim towards achieving pure rolling?friction will always act in such a way to make it pure roll?"

Answer: No. Sometimes slipping velocity increases instead of getting smaller.
It is the case if you put a disc on an incline with low friction (or great angle). Th e disc will slip for ever.

Q2: "I think I heard somewhere that Work done by friction is 0 in pure rolling so that's neutral PE,not sure"

Answer: almost true. It is the case when rolling on a FIXED base. If the base is moving, work done by friction can be +ve or -ve.

Answer 27

Wow! :O by low friction you mean you mean less than _____?
and the angle?nearly 70 degrees?
thanks for the answer btw!

Answer 28

low friction means comparatively.. the disk will keep spinning a lot :D

Answer 29

if it is rotating purely then why kinetic fric??

Answer 30

There will be an inequality between µ and α, depending on mass of body and moment of inertia.

For instance: tan α > µ/3

I will derive an example, but I have no time right now.

"if it is rotating purely then why kinetic fric??"
Answer: No kinetic friction is implied in the case of pure rolling. Only static friction acts (and rolling friction too if it is not considered negligible, which is the case is most problems).