Author Note: This is a one-shot story that takes place during Naruto's training trip with Jiraiya.
It was surreal.
Naruto Knelt in a pool of his own blood cradling the jagged and splintered stump that was once his right hand.
And all he could think about was that day in class 3 years ago when Iruka-sensei had been explaining to them the Laws of Inertia. Specifically the third law: For a force there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.
"What we do may seem like magic but it is not," he had told them. "Ninja are just as bound by the natural laws as everyone and everything else. You must never forget this."
Iruka-sensei had been explaining to the class that the danger's jutsus posed to the wielder were just as real and deadly as those posed to the victim.
True to form Naruto had ignored the lesson in favor of imagining all the amazing jutsus he was going to master on his way to becoming Hokage. He was, on vague level, shocked that he was even able to recall the words spoken after so many years.
But as he sat there on the edge of consciousness, crippled and staring at the remains of the boulder he had used to test the finished Rasengan on( the Rasengan he'd pumped more chakra into then was necessary because he just had to show off); he couldn't help think what a stupid way this was for a dream to die.
Blood loss finally caught up to him and he passed out.
End Note: This is something I've been mulling over for a while. Ninja's in the Naruto-verse, for all their gravity defying chakra fueled wizardry, would still be bound (I think at least) by certain laws. Newton's Third Law and the Rasengan are a perfect example. You're attacking with a dense swirling mass of destruction in the palm of your hand. Even supposing you could regulate the attack so most of the force was directed at your opponent, there would still be a backlash. Especially considering the close quarters nature of the attack. Given Naruto's inattention in class and perpetual state of idiocy throughout the show; this scenario has always seemed likely. Then again this is just a cartoon I suppose and I could have over thought the whole matter. Damn brain.