Rocks and Bottle

Part 1: Two rocks are thrown sequentially at a bottle. Either is sufficient to shatter it. Does the second rock to arrive cause it to shatter?

Your vote: Yes No

Part 2: Two rocks will be thrown simultaneously at a bottle. However, a noise delays the throwing of one of the two rocks. The first thrown rock shatters the bottle. Does the noise explain that the bottle was shattered by the first thrown rock?

Your vote: Yes No