The Rama, Orach Chayim 553, says:
The practice is that we do not study [Torah] the day before the ninth of Av from midday on, except such matters as are permitted [study material] on the ninth…. Also, one should not go on a pleasure trip on the day before the ninth of Av.
(Mishna B'rura comments that others condemn the practice of avoiding Torah study on the eighth, but my question is about the practice to forbid it.) Many practices are forbidden or frowned upon on the ninth: five main abstentions (eating, washing oneself, anointing oneself, marital relations, and wearing leather shoes), sitting on a chair, Torah study, greeting people with a blessing, conducting business, going on a pleasure trip. Why are Torah study and trips singled out as the two things extended to the eighth? I understand that a ban on eating is not extended: that's too difficult, even dangerous. But sitting on a chair? marital relations? greeting people? Why not? What's special about Torah study and trips?