Direction of percieved gravity - MIT lecture

[jsmith613]

http://ocw.mit.edu/courses/physics/8-01-physics-i-classical-mechanics-fall-1999/video-lectures/lecture-5/

starting at about 24 min in this video, Prof. Lewin starts talking about whirling an object around in a circle...now he then says that the direction of perceived gravity in is in the OPPOSITE direction to the centripetal acceleration..
would I be correct in assuming, however, that on a free body diagram, gravity will still be drawn vertically downward?? if not, why?

 

[CAF123]

I watched all of Professor Lewin's lecture series on classical mechanics as preparation of 1st year university. I think the perceived gravity upwards is a result of the (fictitious)centrifugal force. From the perspective of the water, it is not moving in the bucket as it swirled around and so it 'invents' a centrifugal force (reminiscent of one not accelerating in a bus from one's own position) to counteract the centripetal force. Since this force is fictitious, on a free body diagram gravity would still be acting downwards.

 

[A.T.]

gravity will still be drawn vertically downward?? if not, why?

Earth's gravity, yes. by "percieved gravity" he probably means the vector sum of Earth's gravity + centrifugal force in the rotating frame

 

[jsmith613]

Earth's gravity, yes. by "percieved gravity" he probably means the vector sum of Earth's gravity + centrifugal force in the rotating frame

ok thanks