# Projection with coriolis force

1. Nov 17, 2005

hi,

i read lots of book regarding fictitious force - coriolis and centrifugal forces, but i am not clear how to determine the direction of the force..

example. if we throw a ball vertical up , how we can know the deviation from the original position ( from book we know that if the ball drop from a height - it will deviate to east )

pls explain or show the links regarding this two forces

thanks thansk

2. Nov 19, 2005

### Chi Meson

THe Earth's surface is moving toward the east. If you threw a ball straight up, it would initially be moving eastward at the same speed as the earth's surface. Ignoring any air resistance, the ball will continue to have this eastward speed.

As the ball gets higher, it would have to move eastward at a faster speed in order to stay above the same spot on the earth. This is just like the fact that the outside horse on a merry-go-round moves faster than the inside horse because it is at a larger radius.

Since the ball can not gain speed in the eastward direction, it "lags behind" the point on the earth where it was launched. From the point of view of the earth's susrface, it seems as if a force is pushing the ball westward, when actually it is the lack of an easterly force that causes the effect.