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## Main Question or Discussion Point

**centripetal and tangential acceleration in rotational motion....?**

consider a stone attached to a string moving in a horizontal circle in a gravity field.

now it has two accelerations one along the [itex]\hat{r}[/itex] direction and the other along [itex]\theta[/itex][itex]\hat{}[/itex] (theta hat) direction

but there is only one force. the centripetal force and the only acceleration produced as a result of that is the r hat direction acceleration that is the centripetal acceleration directed inwards.

so i suppose that there must be a force in theta direction as well responsible for acceleration in that direction

if all of what i said (which i doubt) is correct then what is that theta directed force?

second question: centrifugal force exists right? so when we cut the centripetal force why does not the stone or ball whatever it is fly off in the direction opposite to centripetal force that is in direction of centrifugal force directed outwards? instead what is observed is that it goes off tangential...what is the reason for that?

last one: i got some notes from my professor about rotational motion in which a ball bearing was placed inside a hollow tube. it was not attached , just placed. so when we started rotating it it moved outwards as well as the rotated, obviously. so it was spiral motion.

if you are getting what i am saying then can you think of any force due to which it moves outwards? i mean the circular part is obvious but why move outward?

there is only one force the contact force by the tube. but that is in theta direc tion and it must be solely responsible for the circular motion. my teacher said that the outward motion part is also associated to the contact force, somehow.

i could not understand him at all on this one.

so if u can think of anything then please do .....thanks