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1. If a person forgets that it is Shabbos and throws an object in Reshus ha'Rabim, and then he remembers that it is Shabbos, he is exempt.
2. Even if he knew it was Shabbos when he threw the object, but the object was caught by a person or a dog or burned while in flight, he is exempt.
3. If a person intentionally throws an object on Shabbos in Reshus ha'Rabim into the mouth of a dog or into an oven, he is liable.
4. One who performs the Melachah of Boneh (building) on Shabbos is liable even if he does a minimal amount of building.
5. One who prepares a stone to be used for building is liable.
A BIT MORE
1. One is liable to bring a Korban Chatas only if he was unaware of his transgression from the beginning of the action until the end.
2. If it was caught by a person or a dog, he is exempt, because two people or entities performed the Melachah, and he did not perform the entire Melachah himself.
3. The person's intent for the object to land in an abnormal place can give the place the status of a normal place. The Mishnah, which says that he is exempt when the object lands in the mouth of a dog, is discussing a case in which he did not intend for the object to land there.
4. Similarly, one is liable for completing even a small finishing touch on a vessel (Makeh b'Patish) on Shabbos.
5. Rav: He is liable for building (Boneh). Shmuel: He is liable for completing a vessel (Makeh b'Patish).
Next Daf Index to Revach for Maseches Shabbos