Hi.

I have a disc sliding on a flat surface with some friction, flat side down. How's its direction going to change if it starts rotating? What formulas describe such motion? Thanks!

Question

Hi.

I have a disc sliding on a flat surface with some friction, flat side down. How's its direction going to change if it starts rotating? What formulas describe such motion? Thanks!

mani_jha · Answer

The direction of motion will be the same, I think. 
This motion which comprises both of translation(straight motion) and rotation is known as rolling motion.
When a body rolls purely(without sliding at all)
$$v=w \times r$$
v is the linear velocity of the center, and w is the angular velocity.

mos1635 · Answer

i am confused....|dw:1333701759667:dw| is that the case?

mani_jha · Answer

The upper one, most probably.

mos1635 · Answer

How's its direction going to change if it starts rotating? !!!!!!!!!!
how is that possible ???

mos1635 · Answer

something in that frasing is wrong or missing......

mani_jha · Answer

Yeah, even I think that the direction will be the same.

anonymous · Answer

Sorry for not being around much after I asked the question - life happened. I meant the 1st case from mos1635's picture. It's a case of the curling stone - making it curl causes it to travel on a curved trajectory rather than straight line. Googling gave me this site with a reasonable answer: http://www.real-world-physics-problems.com/physics-of-curling.html Cheers!

mos1635 · Answer

|dw:1334872121818:dw|
yeap now i got it!!!
have no idea thow...:)