Question: Why is this prohibited?

Answer: It is considered Molid on Yom Tov.

Question: This should be permitted (a food need)!?

Answer (Rabah bar bar Chanah citing R. Yochanan): We are speaking of new tiles which may not withstand the heat, or which are thus hardened into service.

A bird was trampled or was smashed against the wall by a man;

Or it was trampled by an animal and unable to stand up (Mefarcheses);

Such a bird may be slaughtered if it survived 24 hours after being injured (otherwise we are concerned for Risuk Eivarim, even if the examination reveals no defect).

R. Elazar bar Yanai said that even if it survived 24 hours and there is no concern for Risuk Eivarim, the animal must be examined for other defects.

Question (R. Yirmeyah): Is one permitted to slaughter such a bird on Yom Tov (given that he may discover that it has Risuk Eivarim, and the Shechitah will then have been in vain (unlike other animals which are presumed to be Kosher, even before the customary examination))?

Answer (R. Zeira): From our Mishnah (which prohibits the heating of tiles on Yom Tov because they need to be tested) we see that it is not permitted.

(R. Yirmeyah): The prohibition of tiles is owing to the other reason (the tiles are hardened into service) and thus tiles cannot be compared to the Mishnah in Chulin.

Question: There appears to be a contradiction in the Beraisos dealing with partial acts of Bishul!?

One Beraisa teaches that if one person lights the flame, another places wood, a third places the pot on the stove, and a fourth pours in the water, yet another adds spices and another stirs, they are all Chayav (on Shabbos).

Another Beraisa teaches that only the last one is Chayav.

Answer: The first Beraisa speaks when the first person lit the flame whereas the second Beraisa speaks when the last one lit the flame.

Question: What Melachah is done by the one who placed the pot on the stove?

Answer (Resh Lakish): The pot is a new one, and heating it strengthens it akin to the tiles discussed above.

One may move an oven on Shabbos (since it has use like other Kelim) but one may not (even on Yom Tov) smear it with oil or rub it with a cloth.

Cooling the oven with cold water is forbidden if it is done to strengthen it, and permitted if it is to prevent the bread from getting burned.

One may boil the head or feet of a bird in boiling water (in order to remove the hair) on Yom Tov but one may not smear them with lime or earth (as would a tanner) nor remove the hair with scissors (it looks as if he is doing this for the hair).

One may not cut the leaves off vegetables with the clippers with which one usually cuts them from the ground (it appears as though he cut them from the ground on Yom Tov).

One may prepare even those vegetables whose preparation entails a lot of effort and one may heat up and cook (a large amount of food) in a Purni or in a large kettle since that is what is needed.

One may not, however, use a new Purni since it might crack from the heat (and one will have undertaken a lot of trouble in vain).

One may not fan the flames of a fire using bellows since it looks like a professional job, but one may fan the flames by blowing through a tube.

One may not prepare or repair a spit for roasting.

One may not break up a bamboo into strips to use as a base for frying (Tikun Kli) but one may break open a nut wrapped in a cloth, even if there is a chance that the cloth will tear.

(R. Eliezer): One may stand by a Muktzah on Erev Shabbos during Shemitah (when Ma'aser does not apply) and verbally designate parts of it for use.

(Chachamim): Verbal designation is not sufficient (one must mark the fruit that he intends to use on Shabbos) because there is no Bereirah.

Figs which children put away on Erev Shabbos and then forgot about them are forbidden on Motzei Shabbos until Ma'aser is taken (the effect of their being designated as food for Shabbos).

Figs which were put out in one's Chatzer to dry, his family may eat them casually without having to separate Ma'asros (a Chatzer is only Kove'a fruit for Ma'asros if it is ready to eat not those put out to dry).

Question (Rava): Does Shabbos cause Muktzah (which is not yet completed) to become Kavu'a?

Answer (R. Nachman): Shabbos is Kove'a.

Question (Rava): Shabbos should be no stronger (as a Kove'a) than a Chatzer (which is only Kove'a that which is ready to eat)!?

Answer (R. Nachman): We have a tradition that Shabbos is Kove'a whether the food is, or is not, ready to eat.

(Mar Zutra bar R. Nachman): Our Mishnah supports my father's teaching since R. Eliezer permits verbal designation on Erev Shabbos during Shemitah, implying that, on any other year of the cycle, verbal designation would not help (which indicates that Shabbos is Kove'a even by something, like the Muktzah, which has not yet reached the stage of Ma'aser).

We refute this proof by asserting that it is not Shabbos that fixes there, but the verbal designation that he made.

Question: Then why does the Tana need to mention Shabbos (the same will apply on a weekday)?

Answer: The Tana teaches us the additional Chidush that Tevel is Muchan on Shabbos (since Min ha'Torah there is no Isur of separating Ma'asros on Shabbos and Yom Tov, it is technically Muchan).