Physics problems, like if I hit the couch with my fist and used 100N of force, the couch will give m

When it comes to impulse, impulse = force t, the sofa has a cushioning effect, so t is relatively large. And the impulse = the change of momentum, you have the same force, and the change of momentum in the past is the same, so the impulse is the same. This is the first formula, the same impulse, the greater t, the smaller the force, so you won't feel pain when you hit the sofa, but you will feel the same when you hit the wall....

I guess so...I almost forgot about it.

Or a force of 100N.

Because the force hitting the couch and the reaction force that the couch gives you are a pair of interaction forces, and the interaction forces are always equal.

Hitting the wall because the wall can only undergo a slight deformation, the contact area between the fist and the wall is smaller than the contact area between the fist and the sofa, and the force is equal, so the pressure of hitting the wall is better than hitting the sofa, so it will hurt.

First of all, you don't have a dynamometer, so you can't guarantee that you will use 100N force to hit the sofa and the wall. Secondly, even if you can ensure that the force is equal, because the sofa is soft, the contact area is relatively large when hitting, so the pressure is small, and the pain is relatively weak.