beat on (something)
To strike something repeatedly. Quit beating on the door, I'm coming! I've been beating on at that nail and still can't get it to go into the wall. How much longer will your little sister beat on the piano tonight? I'm getting a headache from all that racket.
beat on someone or something
to pound or hammer on someone or something. She beat on him until he let her go. Stop beating on that drum!