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When Jiraiya used Rasengan on a tree, it shredded part of it and trees are not soft. They are so much harder than human flesh. However, the first time Jiraiya used it on a gangster, he didn't die.

Why is that? He should have been torn to shreds.

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    Well, it is just basic chakra balance i guess. If you remember Kakashi's first lesson about chakra (during the Kiri arc), he said that jutsus will fail if the amount of chakra used is to low or too high. Jiraiya probably protected the life of his opponent on purpose
    – Nevios
    Aug 9, 2017 at 7:30
  • Doylist explanation: Jiraiya is supposed to be a good, if a little pervert, character. Him killing people that are vastly inferior to him in terms of power would leave the wrong impression.
    – Annatar
    Aug 9, 2017 at 12:07

3 Answers 3

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When the Rasengan makes impact, there are two effects that take place

The first effect is

On contact, the Rasengan grinds into its target, propels them along the Rasengan's trajectory - either away from the user or into the ground beneath them

When Jiraiya used the Rasengan against the gangsters, this what we saw.

The second effect is

and at some point bursts, causing severe damage at the point of contact.

The burst is what truly deals the damage. Jiraiya mastered the technique of the Rasengan and more than likely had control over it for it to not burst.

Anyways, he was trying to make a point and get the gangsters off of his back - there was no need to kill them. Jiraiya even says

And I was holding back. You guys are hardly worth the trouble

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Chakra is an energy, meaning that it may appear that in both cases Rasengan is the same but not the same amount of chakra. Apart from this, the tree is grounded and can't move, and when a Rasengan hits a person (basically Rasengan is a rotating chakra), the person moves and the impact is not full.

It's explained in Physics.SE

Well, force will be a function of time.

Force is a function of time

So, while we can't find the force (a meaningless quantity), we can find how the force varies over time. For example, if the body the object crashes into obeys Hooke's law/Young's modulus (and the object is rigid), we can calculate force by solving:

Second force equation

illustration of force

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  • It's really hard to compare physics concepts in Shinobi world. If you really want to give better answer then try to join some facts from Naruto series or Manga but yes I agree with the amount of chakra answer. Also in animation it would be really awkward if we can see any person getting shredded into pieces with Rasengan so maybe that's why they avoided it. Aug 9, 2017 at 11:40
  • @LightYagami Kabuto was,but still he wasn't grounded.The force of the rasengan was greater than his weight....this was the right equation: RASENGAN POWER > OBJECT WEIGHT in order to move the object
    – user35052
    Aug 9, 2017 at 11:50
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Naruto hasnt taken the full amount of time to gather the energy needed in order to fully hand out the highest amount of damage possible with his Rasengan. As he progresses through his practices he grows stronger because hes learning how to fully use his Rasengan. The more he learns, the easier and stronger it becomes.

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  • This question is about Jiraiya's Rasengan, not Narutos Aug 10, 2017 at 18:41

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