碰在钉子上

hit a snag

碰破皮

get a knock and graze one's skin

碰破头

break one's head

碰上地雷

hit a landmine

把人碰倒

knock someone over

把椅子碰倒

knock the chair over

小孩子碰哭了。

The child got a knock and started crying.

腿在门上碰了一下

hit one's leg on the door

他用胳膊碰了我一下。

He gave me a knock with his arm.

箱子里装的是玻璃器皿，一碰就会碎。

The box is filled with glass things; they will break if they are knocked.

突然碰上了个机会

suddenly presented with an opportunity

突然碰上警卫队

suddenly run into some guards

碰碰运气

try one's luck

这要碰碰看。

One needs to try this and see.

碰碰看，也许能行。

Try it and see, it might work.