The Coriolis Effect

I wanted to try to understand the Coriolis effect. My curent thinking uses a simplified model of an object moving across a rotating disk. To avoid complications with centrifugal force it will move from the outer edge of the disk towards the centre. The effect of centrifugal force should then just be to slow it down, ultimately throwing it back out to the edge again. However, when we take the Coriolis effect into account it will also drift sideways. To simplify the work:

• The object is in the air while travelling across the disk so it is not affected by the centrifugal force at all
• We will also ignore air resistance.

With these simplifying assumptions the only effect left is the Coriolis effect.

So the model is:

1. The object leaves the outer ring of the disk with a fixed angular velocity.
2. It is also travelling towards the centre with a fixed velocity.
3. As it moves inward it has a greater angular velocity than the part of the disk directly underneath it.
4. So at each stage it will run ahead of the lines of longitude passing below it.

We will rotate the disk anti-clockwise. This means that the lines of longitude to the left of the particle will rotate round towards the particle. Running ahead of the lines means the particle curves to the right. This is a model of the Northern hemisphere of the Earth.

Method

At each moment of time t, the particle has arrived at the next line of latitude. It has also travelled a total distance of vt. We will draw an arc from each of the preceding lines of longitude. The ends of the arc show the apparent path of the object.