A was banging her hand on a plastic table when she questioned me: will the table break if I do this way?

Me: No

A: will it not break when I keep hitting?

Me: if you hit it hard, it will break, not when you slightly do it.

A: am I hitting hard on the table?

Me: no, not really. You are light on it.

The child doesn't know what is meant by hitting hard or light. Parent needs to explain what exactly is hard before yelling (but, do not yell) at the child for banging hard on something.

So, next time, when your child is banging on something, show it to him what exactly happens when something is hit upon. How is the pressure carried forward. That is exactly how I have explained A whenever I had to convey her the consequences of something that may hurt her.

When she is jumping around something sharp or hard that could hurt her, show her that edge which is sharp, rub your finger against it and with appropriate expressions tell her it would hurt if something sharp is rubbed against.

When the child is hitting on a plank that most likely would break, show him how the plank would bend as you slightly press against it and tell that excess pressure would ultimately break it down.

One may think that reacting in a rush in order to stop the child from what she is doing actually worked. It might have just worked at that moment but is not a beneficial solution in the long run.