Thanks for the reply tinytim :)
The fact that in an inertial frame, [itex]\ddot{r}[/itex] is positive is what bothers me ... How can the block, physically speaking, move if there is no force responsible for its radial motion ? I understand your point mathematically but I still have some trouble understanding it intuitively :/
And also, what is the meaning of the block having a zero radial acceleration component while it is still moving radially ? Again, the mathematics of it make sense to me, but its physics is what confuses me the most ... What is the real meaning of radial acceleration ?
