How to say "collide" in Japanese

• ぶつかり合うぶつかりあう
  godan verb, transitive verbCovers the physical sense of 'collide', with the nuance of two or more things crashing into each other mutually. Best when the collision itself, such as vehicles or bodies hitting head-on, is what you want to describe.
• かち合うかちあう
  godan verb, intransitive verbCovers 'clash' and 'conflict' more than literal collision, and can also mean two things coincide, such as events falling at the same time. A less common choice for physical 'collide', so it seldom suits object crashes.
  試験しけんの日ひが私の姉あねの結婚式けっこんしきとかち合あった。↗

  The date of the examination clashed with my sister's wedding.

For physical crashes or mutual collisions, 「ぶつかり合う」 is the direct choice; 「かち合う」 covers clashes, conflicts, and coinciding events, so use it when the sense is collision of schedules or interests rather than objects.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• ぶつかり合うぶつかりあうto collide
• かち合うかちあうto clash