碰撞：crash 碰上某人：meet somebody by chance 撞上某人 has two meanings: 1)crash into someone for example, I was stumbled and I crashed into a person. 2) meet somebody who u dont want to meet by chance for example, A man is screwing around a woman while the husband of the woman meets them......we can say: 一个男人正在和一个女人×××，正好被女人的丈夫撞见了。 ofc u can change this phrase a little to use 撞上某人

碰上某人是指，遇到某人，happen to meet somebody. 撞上某人指，run into somebody

- Generally, 碰 means touch, 撞 means crash, bump.. - Sometimes 碰 and 撞 means bump into; run into; meet by chance; come across. but 撞 especially means you meet someone that you don't want to meet.

- Generally, 碰 means touch, 撞 means crash, bump or strike - sometimes 碰 and 撞 means bump into; run into; meet by chance; come across, but 撞 especially means you meet someone that you don't want to see.

"碰到某人"的話， 1. 同"遇到某人" 2. touched sombody，大多是輕輕地接觸到，沒有"撞上/撞到"那麼痛