# Inelastic Collisions

ehild
Homework Helper
cyrusabdollahi said:
no ones responded to if I am correct or not about the initial force upon and object being depedent or indepent of the material used.
The initial force, the force at the moment of inpact when the colliding bodies just start to interact, this force is zero.

ehild

very interesting. How can this be? I thought the moment they touch eachother, they will feel equal and opposite forces. This would imply that they touch without either one feeling any force. It would seem logical that the first instant of impact would be where the most force is delivered to the body. Such as if i punch a wall, i would feel it most the instant my hand hits the wall, since it is moving the fastest.

ehild
Homework Helper
cyrusabdollahi said:
very interesting. How can this be? I thought the moment they touch eachother, they will feel equal and opposite forces. This would imply that they touch without either one feeling any force. It would seem logical that the first instant of impact would be where the most force is delivered to the body. Such as if i punch a wall, i would feel it most the instant my hand hits the wall, since it is moving the fastest.
Try. Move your fingertip quite close to your display so as just touch it. How much force do you feel? Then go on moving. What do you feel?

ehild

So I wonder at what point would you feel a maximum force?

i tink u mis understood the conservation of linear momentum. it says whenever u one object having mass m and velocity v collide with another then the momentum of that body will be the same mv. if its heavier then it will have less velocity and if its lighter then it will have more velocity.

no I understand that part, but its not what im talking about. Im talking about the interal forces that are exhanged during a collision.

Hmm, I have another question. How come we know that the area of the internal forces that take place during a collsion always sum up to be the same. I know that the two bodys experience the same force for the same amount of time, but what I am talking about is from one experiment to the next. Example, If i have a cetrain projectile inelastically collide with another, they will stick and move off together, and their momentum beore will be equal to that after. Now, lets say I have a heavier projectile but moving slower, so that the momentum is the same as in the first experiment, then they two will inelastically collide and move off together in the same direction with the same amount of momentum as when we started. Now according to the conservation of momentum, the area that is underneath both curves of forces for time in both experiments will be equal. My question is how do we know that they will be equal from one experiment to the next. My problem is that, if I were newton and I said ok these have equal forces for equal amounts of time that would be acceptable for one case of an experiment. But this formula alone is not enough to let me conclude that for any other inelastic experiment of equal initial momentum will encouter the same area in the force curve. Is this something that was determined through experimentation, or was newton able to say that friction plays no role in momentum exchange without ever having to do a single experiment?