1. Work = Force X Distance
2. The principal activities involved in building the Tabernacle.
3. An act that results in a significant increase in the utility of an object.

Incorrect. The Torah does not use the term "Avodah", which denotes physical exertion and would be similar to the scientific definition of work. The term used is "Melacha", which implies a more subtle form of work, similar to its use in regards to the building of the Tabernacle, where "Melacha" means "skilled, creative activity".

1. Work = Force X Distance
2. The principal activities involved in building the Tabernacle.
3. An act that results in a significant increase in the utility of an object.

Correct. The prohibition of "work" on Shabbat is juxtaposed four times in the Torah with the building of the Tabernacle (Exodus Chs. 31, 35; Leviticus Chs. 19, 26). This suggests that the actions involved in building the Tabernacle are those very actions that are forbidden on Shabbat.

The Oral Tradition lists 39 major categories of actions prohibited on Shabbat, which were the 39 major categories of "work" in construction of the Tabernacle.

1. Work = Force X Distance
2. The principal activities involved in building the Tabernacle.
3. An act that results in a significant increase in the utility of an object.

Correct. The Torah teaches us that we are not absolute masters over the world, by restricting our interference with the natural world for one day a week, Shabbat. The 39 prohibited categories of "work" all result in a significant increase in the utility of some object (e.g. cooking), thus showing our mastery over the world by constructive exercise of our intelligence. It is precisely this that is forbidden on Shabbat. (Rabbi S.R. Hirsch)