0
$\begingroup$

I searched and viewed similar questions on here but still am very confused. Is it because of the observer's inertia? If so, shouldn't we feel a 'push' towards the point where we are actually accelerating?

Also, why would a small rock on a rotating disk be pushed towards the outside? The only force acting is inwards so why would it go outwards? It makes no sense to me. I appreciate your help truly. Sorry I am an amateur and not an expert.

$\endgroup$
1
$\begingroup$

Draw a tangent to the disk at a point. the rock has tendency to move along such a tangent at each instant(due to its inertia). hence it feels as though it is pushed outwards w.r.t. the disk. and for the same reason it needs a force along the radial direction to keep up with the disk.

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ thanks a lot. I now I understand its because of inertia. Is there a simple reason why its directly in the opposite direction of the acceleration? $\endgroup$ – mathstudent132 Jul 23 at 4:44
  • $\begingroup$ the rock's motion is not in the opposite direction of the centripetal acceleration. The rock when viewed from the disk's frame appears to be moving in the opposite direction. it just wants to move along the tangent(inertia). $\endgroup$ – Pranay Jul 23 at 5:19
  • $\begingroup$ @Ohw i think you've misunderstood what i have written. The rock's velocity is along the tangent direction. hence, it has tendency to move along that direction. $\endgroup$ – Pranay Jul 23 at 6:05
0
$\begingroup$

What force an object is experiencing depends upon the reference frame of the observer. If you sit in the rock's frame (the one which is rotating), the only force acting on it (excluding frictional forces at contact) is fictitious centrifugal force which directs outwards away from the disk's centre.

Generally speaking, fictitious force comes into the picture when you go from an inertial frame to a non-inertial one.

So in stationary frame, how do you explain the rock moving away since outward force is not there? Observing in stationary frame, you see the rock follows percievably a different path. What keeps the rock rotating is a force (centripetal) directed towards the centre. This can be provided by the friction between rock and disk surface. If this force suddenly vanishes, the rock will follow a straight line motion. This motion when viewed in rotating frame appear as if the rock is moving away from the centre.

| cite | improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.