Yuri is standing on a hill holding a ball. He is facing downhill. Mei is standing at the bottom of the hill facing up towards Yuri. If Yuri rolls the ball down the hill, will Mei be able to see the ball coming towards her the entire time it is rolling down? Respond very briefly.
Mei will be able to see the ball coming towards her as long as there are no obstacles on the hillside obstructing her line of sight. The ball, rolling downhill due to gravity, follows the curvature of the hill, and since Mei is facing up the hill towards Yuri, she will observe the ball roll down from his position to hers. If any part of the hill between them is steep enough to occlude her view, then there may be moments when she cannot see the ball. Assuming a regular, unobstructed slope, Mei will see the ball the entire time it is rolling down.