you concede that now the park isn't moving in a circle dr humans exerting a force to keep it moving in the circle and you can see this from the fact that the rubber ring is extended heat is exerting the center of the billboards and this is the only horizontal force acting on the part but not let's look at it again from his point of view in the rotating system he is exerting a force towards the center of the table and yet the puck is standing still produced more or less taylor some vibration how he believes in a lot of inertia so he thinks there's and equal parts on the part away from the center of the table so that there is no unbalanced boring this outward force in the pocket the fictitious sports in this case sometimes it's called the centrifugal force in the pics reference frame there is no award boris on the path now suppose the doctor doom stops exerting a barge watch the pot in the picture frame of reference the puck moves off in a straight line there's no no unbalanced boris acting on it now let's look at it again from his point of view in the rotating system when he releases the proc which to him was everest it mood the force away from the sender is now on unbalanced part on the talked to him the outward course on the part is fictitious in our food frame of reference it doesn't think that's but the doctor whom in the accelerated frame of reference it's a perfectly real force i hope by now doctor i do not have convinced you the rotating frame of reference is not in their shel frame for you've all been told that the hurt it's rotating abode of taxes and that also it travels in a nearly circular orbit around the time why then do we find in a frame of reference attached securely to the earth but the law of inertia seems to hold why don't we observed fictitious forces the five of the fictitious forces which we have to introduce in a non initial frame depends upon the acceleration of the frame these smaller the acceleration is v smaller the fictitious forces that we introduced here's a frame of reference attached to the equator of the car the acceleration of this frame is really very small because bearded spinning about it axis it has an acceleration directly inward app three d_ one hundred of a major per second square on they one kilogram at the equator their is the fictitious for us directly upwards out three one hundred but this is not by gravity which is a port downward of nine point eight new so the net downward force is smaller than that of gravity alone if i've dropped av one kilogram at the equator the acceleration would be slightly smaller than that due to gravity alone very much now the acceleration of the car in its orbit is even smaller still and produces even smaller affect in our frame of reference mike said that the earth was rotating abode faxes how do we know but this is slow well if you take a time exposure photograph of the stars they seem to be moving in circles a both p pole star but all motion is relative is there any way of telling which is moving or the stars the fact that it is because which is rotating can be demonstrated by means of the pendulum if i've got a pendulum swinging its wings back-and-forth in a plane though it turns out is this pendulum with the north pole of the art the plane of swing would remain fixed relative to the stars but would rotate relative now i'll have to show you what i need this pendulum is epicenter how this turntable which will represent europe no i was about the cable turning around in this direction i'll put a black arrow on so that you'll remember but the rotation the pendulum is that the north pole of the earth annuals motion as you ordinarily do standing on the earth the playing of swing rotates in the opposite direction from the rotation of the turntable and that exactly the same rate now look at it from the fixed cabral which will represent the frame of the stars the turntable the alert rotate but the plane of the pendulum remain specs a pendulum used for this purpose because approval pendulum use tommy dot wong at the beginning of this film