Question

lec 5 wen prof lewin ntold abt the marble in the smooth tube which cannot give the marble the centripetal accelaration that it requires he says it moves up but it should stay where it was as there is no force acting on it neither it does have any velocity

Answer 1

He says it has an initial velocity straight up... and that that is why it moves up

Answer 2

and wat will happen when it reaches the bottom then it will have centripetal accelaration right because of the force that the bottom of the tube will apply on it

Answer 3

wat abt the lettuce drying experiment,in that case water is initially at rest so it should not move but if we take the concept of percieved gravity then according to it water should come out and the same is happening over there,so it should be the concept of percieved gravity that should be the reason behind the drying the lettuce but prof lewin says the water is like the marbles

Answer 4

so we can say that its the percieved gravity which is actually behind this drying of lettuce and this experiment of drying the lettuce has nothing to do with that marble one,right?

Answer 5

when it reaches the bottom of the tube, it will have centripetal force, correct. In the case of the lettuce, the holes in the colander allow the water to continue in a straight line, but the lettuce is retained because it can't fir through the holes. In cases of circular motion,. the perceived gravity is equal/opposite of the forces required to make the object go in a circle

Answer 6

but water that is on the lettuce does not have any initial velocity

Answer 7

neither does the lettuce... but he gives it an initial velocity by swinging it. you're making this too hard... all he is trying to show is that the lettuce which eventually experiences a centripetal force stays in the colander but the water which makes its way outward eventually finds a hole and at that point doesn't experience a centripetal force, thus exits the hole goes into free fall (projectile motion)

Answer 8

FINALLY understood...thnx