Carousel...?

Question

Peter and Danny are standing opposite of one another on a carousel which is turning counterclockwise. Peter throws a ball directly towards Danny.

a) The ball gets to Danny.
b) The ball goes to the right of Danny.
c) The ball goes to the left of Danny.

The answer is b. The ball might start going directly towards Danny, but by the time it gets that far he and the turning table will move, so the ball will miss him. The table turns counter-clockwise and threfore as the ball speeds towards Danny, he has already moved to the left, resulting in the ball passing to his right as it flys over the place which was previously occupied by Danny. So the ball goes to the right side of Danny.

Moreover, en if Peter aims the ball at Danny it does not even start going towards Danny when Peter throws it. Why? Because Peter is not standing still. He is moving with the carousel. The ball carries with it Peter's velocity, that further deflects the ball towards the right.

When you live on a turning world things do not go in the direction they are aimed. In fact, they don't even SEEM to go in straight lines.

This deflection has a name. It is named after one of the first persons to study it -- Coriolis. There is even a slight Coriolis effect on ...

things moving over the earth because the earth is truly a turning world.

Suppose you forced the ball to go from Peter to Danny. How could you force it? By making it go in a pipe which started at Peter and ran to Danny. The pipe is straight, but turns while the ball is on its way. So even though the pipe is straight the ball moves in a curved path. It takes force to make a thing curve. The heavy-lined side of the pipe must exert the force on the ball. Do Peter and Danny think the ball curves? No. They move with the turning pipe. So they think the ball just goes straight -- yet they must wonder why it keeps pushing on the side of the pipe. Of course once they realize they are turning the wonder is explained.

Answer 1

This best illustration of Coriolis force I have seen(1).

Oh yea its is (c)
if it was clockwise it would have been (b)

Answer 2

I think the important thing about the Coriolis "force" is that, in the carousel example, it is only apparent, not real. If viewed from an inertial nonrotating coordinate system the ball moves in a straight path at constant speed. It's the rotation of the coordinate system that produces this apparent force, which is only tangible when the ball is accelerated away from inertial straight-line motion, for instance by friction or being constrained to run on a straight track on the carousel. For me this basic and simple mechanical explanation is the key to understanding the phenomenon.

Answer 3

Both b and c are correct. Assuming the boys are facing each other, the ball goes to the right of Danny, looking from Peter's viewpoint, but Danny sees it go to his left.

Each boy is moving to his right, and so is the ball before it is thrown. So when one boy throws a ball across the circle, it will have a component of velocity to his right which will cause it to pass the center on the right.

Looking at it another way, each boy is moving to his right, and sees the other moving to his left. If he doesn't compensate for this motion he will obviously miss, and be off to his right.

Answer 4

If the ball is thrown relatively slowly it will go to the left of Danny.

Answer 5

It's C (viewed from Danny's point of view! - from Peter's it's B).

wmg
(with many greetings ;-))