“Kali Tzom,” Pills, Drops
1. "Kali Tzom" pills and the like are made from concentrated food supplements and have an immediate benefit. Thus, strictly speaking, taking them is not a problem of refuah or preparing for the week. Still, lechatchila it is best to crush the pill and mix it with food or pour the liquid into food before Shabbos so it is not clear it is being taken on Shabbos. If one did not do this, he may mix it into a food or drink on Shabbos and eat/drink it (הגר"ש וואזנר, קו' מבית לוי, בין המצרים עמ' מ"ד ). However, slow delayed release Advil or caffeine pills which don’t have an immediate effect, should not be taken on Shabbos and should be rather taken on Tisha B’Av itself in a permissible way (see below 42).
2. When eating on Shabbos, one may eat more than usual, but he should not say he is eating a lot to have strength for the fast; that is like preparing for the week with speech (מ"ב ר"צ סק"ד ).
Taking a Walk on Shabbos
3. On Tishah B'Av, one should not take a walk outdoors lest it lead to levity or frivolity (שו"ע תקנד סכ"א ). One should also not take a walk on erev Tishah B'Av (רמ"א תקנג ס"ב ) so that he does not lose focus of the aveilus.
4. Erev Tishah B’Av on Shabbos. When Tishah B'Av falls on Sunday, one should not take a walk with other people on Shabbos in a garden or orchard after chatzos lest it lead to levity or frivolity. However, one may take his children to a local park as usual.
Learning Torah
5. In a regular year, the minhag is to only learn topics which may be learned on Tishah B'Av starting at chatzos of erev Tishah B'Av (רמ"א סי' תקנ"ג ס"ב ). The poskim argue whether one may learn as usual on Shabbos when it coincides with erev Tishah B’Av [or Tishah B’Av itself] (מ''ב שם סק''ט ), or whether one may only learn topics that can be learned on Tishah B’Av itself (חזו''א, ארחות רבינו ח''ב עמ' קל''ו ).
6. In practice. One should be machmir in public. Thus, a Pirkei Avos shiur should not take place on this Shabbos (רמ"א, הגריש"א תור ת המועדים סק"ה ), but there are poskim to rely on to be meikel to learn alone or with a chavrusa (ט''ז, מ''ב שם סק''י ). Learning within an "Avos Ubanim" framework is not considered public learning since each father only learns with his son (תורת המועדים שם ).
Seudoh Hamafsekes
7. One must daven Minchoh early enough that he can finish his seudoh shlishis before shkiyoh.
8. Out of honor for Shabbos, the usual halochos of the seudoh hamafsekes – eating just one food, sitting on the floor, eating bread with ashes, etc. – do not apply. One may eat meat, drink wine, make a meal fit for a king (שו"ע סי' תקנ"ב ס"י ), sing zemiros as usual (שו"ת אג"מ ח"ד סי' קי"ב ), and bentch with a zimun (מ"ב סק"י ). However, the seudoh should not be a gathering of friends (מג"א שם, מ"ב סקכ"ג ).
9. Although we do not fast on Shabbos, one must stop eating and drinking by shkiyoh (רמ"א שם ). This should be announced publicly so that people do not think it is like any other week (מ"ב סקכ"ד ).
10. The issur to wash also takes effect at shkiyoh. However, one should not remove his shoes or sit on the floor until it is actually Motzei Shabbos (רמ"א סי' תקנ"ג ס"ב ).
