I need help setting up. Physics Question.

Question

idku · Answer

In the game of tether-ball, a 1.25 m rope connects a M= 0.780 kg ball to the top of a vertical pole so that the ball can spin around the pole as shown in the figure below. http://i.imgur.com/Tb0DjOD.jpg ((Copy paste, don't click, just in case...)) What's the speed of the ball as it rotates around the pole when the angle θ of the rope is 36.0º with the vertical?

ganeshie8 · Answer

Hint :

The ball is in circular motion in the horizontal plane. So, there must be a centripetal force on the ball, which pushes the ball continuously towards the center.

idku · Answer

Yes,

$F_c=mv^2/R$

ganeshie8 · Answer

Yes, but who is providing that force ?

idku · Answer

The weight, perhaps?
I am sorry, I am not sure.

idku · Answer

Thanks for helping:(

ganeshie8 · Answer

Nope, the weight is always perpendicular to the motion of the ball. So gravity cannot do any work on the ball.

ganeshie8 · Answer

Imagine you're that ball. 

Don't you feel the rope pulling you along the rope ?

ganeshie8 · Answer

You're pulling the rope towards you.
The rope pulls you towards itself. 

This type of force is called "tension"

ganeshie8 · Answer

Lets find out tension in the rope first

idku · Answer

Tension is m*g ?

ganeshie8 · Answer

Start with FBD on the ball. What are all the forces that are acting on the ball ?

idku · Answer

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