- 90

- 6

- Homework Statement
- Let's suppose that I have a ball attached with a string, and I'm making it spin.

- Homework Equations
- Newton's equations

If a "stand" on the ball, I would feel a centrifugal force, which would be pulling me out of the circle. But in the equation of centrifugal force we have ##\vec r##, which is the vector that goes from the centre of the non inertial frame to the body in motion. But if I'm on the ball, my system is the ball, and the distance from the system (the ball) to the particle (the ball) is zero, so why do I feel centrifugal acceleration?

Then, if I want to consider the centrifugal force of a body falling from a skyscrapper, which would be the direction of ##\vec r## that I should consider? From the body to the centre of the Earth, or from the centre of the Earth to the body?

Then, if I want to consider the centrifugal force of a body falling from a skyscrapper, which would be the direction of ##\vec r## that I should consider? From the body to the centre of the Earth, or from the centre of the Earth to the body?