He is trying to impress you be making himself look strong by pretending to feel no pain.
Usually it mean's she wants the D.
Your classmate may be showing affection by punching you in the arm.
Then he has a thing for you girl.
She likes you.
Like normal punching but move your arm faster
no it means hes a player
The way you could measure the mass of your arm is to place it in a tub of water that is filled to the brim, and then measure the amount of water that is displaced (spilled over) after you submerge your arm. That would give you a close estimate. But, when you punch, it is more than the mass times acceleration that is delivered, like in Newton's Second Law of Motion. If you watch Bruce Lee punch, you can see that he used his whole body and thrust his hips into the punch.
It means he has a crush on that girl.
sometimes guys punch you in the arm not a hard violent punch a little love tap!
Then she has jealous issues. Arms are safe territory I would say.
Neurofibroma in your arm gives you pain while you try to punch the opponent. In that awkward movement, you invite the actual punch from your opponent.
arm y it mean arm