What are your favourite classical physics puzzles?

[guv]

@wrobel I missed the part $\omega$ is parallel to the plane.

 

[A.T.]

wondered if people would like to share some fun problems that you can snuggle up to on a cold Winter's evening?

There is a sailing race down a river which flows at 10 km/h.

- On the first day the wind relative to the ground blows at 10 km/h parallel to the river in the downstream direction.

- On the second day there is no wind relative to the ground.

During which day can the sailboats make faster progress down the river?

 

[Charles Link]

I believe the correct answer for @A.T. 's sailing puzzle is the second day.
(I've done a little sailing, and to head into the direction the wind is coming from, you zigzag toward the destination).