googly from ATGS

suppose a CD is purely rolling on the floorjust imagine the balance....
the outer radius is R and inner radius is r

after one complete rotation the initial pt of contact with ground again comes in contact with the ground...thus it travels a linear distance of 2Ï€R

also the lower most pt on the hole again comes to its lowermost position again.....distance travelled is 2Ï€r

now as the linear dist travelled by both pts must be equal, 2Ï€R=2Ï€r,
giving, R=r which is absurd.....

so the question is where was i wrong???????????????????

42 Answers

49
Subhomoy Bakshi ·

look at your reason man..............u just missed by centimetres.......at leaast according to me.....ca u detail ur discourse??????

49
Subhomoy Bakshi ·

@karna....yes...

23
qwerty ·

v=rw ...

omega is same for both points ....but radius is different ...so v i.e linear speed and thus linear distance covered by both points is different!!

49
Subhomoy Bakshi ·

kya........r u sure that the linear distance by outer point is 2Ï€R????????then whats the prob with inner pt????????????

well mai sirf gol gol ghumaraha hu..... u r a step behind the answer i thought of...

23
qwerty ·

xyz wats d green line ??
the inner point shud finally shud be at the same initial position ....

49
Subhomoy Bakshi ·

xyz u r wrong in the sense that the inner pt was just above the pt of contact at both initial and final positions......

23
qwerty ·

but wats wrong with #2

1
xYz ·

kk................
@qwerty
v=Rw
w=v/R
velocity of inner point at start = v-(r/R)w

49
Subhomoy Bakshi ·

i already said that linear speed is same 4 both......as they travel equal distances in equal time....u were proceeding quite beautifully in #2 bt ultimately sab makha diya......

1
xYz ·

@atgs the linear speed is variable of time for a particle in the rim of the wheel..............
it is not constant =v
for eg a t=o net linear velocity of point in the bottom post is 0
and net linear velocity of point at inner bottommost point at t=0 is
v-(r/R)w

23
qwerty ·

...lolz ..we know the reason ..subhomoy also knows the reason ..wo sirf gol gol ghuma raha hai ...aur maza a raha hai .. lollll

49
Subhomoy Bakshi ·

but think of average speed they r all equal......i think it is time i should post the answer....shall i?????????????

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