Did Chiaki drop the walnut on purpose in the science room?

Did Chiaki drop the walnut in the science room on purpose to prevent makoto's death in the first place? When she was first in the science room the outside door was mysteriously locked then she fell clearly due to Chaiki running off, can it be that Chaiki dropped the walnut on purpose to prevent her death? (if you freeze frame the movie you can see chiaki's silhouette as she fell down so he saw her charging the walnut, makoto even later accused him of tripping her).

The second time she entered the science room, no walnut was dropped on the floor since she no longer have the risk of dying, instead kouske now have the bike. When she ran to the train crossing, no accident occurred and right after Chiaki called her questioning her if she had been time leaping, so it is probable Chiaki used a time leap to save kouske, but that was then reversed when makato wasted her last time leap, and chiaki then have to use his last time leap.

After the third time she was in the science room she brought the used walnut to chiaki, chiaki first asked "where did you find it?" then quickly asked "No...do you know what it is?", since he already knew where it was (the first question should be more important if chiaki was unaware, if you know what I mean).

For me it seems chiaki dropped the walnut in the science room for a purpose and he wrote "time waits for no one" on the board to warn makoto of the consequences