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I would like to understand the effects of hardness on impact. If you increased the hardness of a hammer (all else being equal) would it apply a stronger impact?

Or would this depend on other factors, like the hardness of the target-object being hit with the hammer?

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The force between a hammer and the surface being struck (assuming that it doesn't break) is more or less equal to the change in the hammer's momentum due to the collision divided by the collision time.

All other things being equal, increasing the hardness of the hammer would decrease the amount of deformation the hammer would suffer, which would decrease the collision time and increase the average force between the objects. Increasing the hardness of the object being struck would do the same thing.

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  • $\begingroup$ Thank you for confirming this. It is no doubt complicated as to how much hardness decreases the collision time. $\endgroup$ – Johnny Sep 19 '17 at 9:21
  • $\begingroup$ What you're describing is the stiffness, not the hardness. Stiffness is the resistance to elastic deformation; hardness is the resistance to permanent deformation. But perhaps the original post by @Johnny is also referring to stiffness, not hardness? $\endgroup$ – Chemomechanics Sep 19 '17 at 16:03
  • $\begingroup$ @Chemomechanics Well, I assumed more hardness necessarily meant more stiffness, unless you changed the construction of the object. Is this true? If so, my suggestion would be to add a, "assuming the stiffness increases with the hardness" to the answer to cover this. $\endgroup$ – Johnny Sep 19 '17 at 20:55

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