For each of the following collisions, argue for or against the collision being a

Question

For each of the following collisions, argue for or against the collision being at least approximately isolated. In each case the system is indicated. If the collision is not isolated then explain what external force(s) cause it to not be isolated. (a) A billiard ball is rolling along on a pool table. It collides with another billiard ball that is sitting stationary in the middle of the table, with no other billiard balls near it. [System: two billiard balls] (b) The same two billiard balls collide again, but this time the stationary one is in contact with the side of the table during the collision. [System: two billiard balls] (c) Two ships collide. The ships are in the middle of the ocean. Both of their engines are running (i.e. their propellors are turning, pushing both ships forward) and the whole collision takes a rather long time (the buckling of the ships hulls lasts for several seconds before the collision is over). [System: two ships]

Explanation / Answer

The collision occurs between two object is an isolated system if the total momentum of the system is conserved...that means momentum of the system before collision and after collision is equal i.e momentum lost by one object is equivalent to the momentum gained by the another object with which first object collide.

for isolated system, net external force on the system is zero, only internal forces acting on collision that changes the momentum of the object.

a) if the friction is so small compared neglible change in momentum then the collision of the billiard ball is an isolated system.

the only unbalanced forces acting upon the two balls are the contact forces that they apply to one another. these two forces can be cosidered as internal forces since they result from a source with in system.

momentum is coserved here.

b) here system is not isolated because friction between biliard ball and side of the table gives the external force i.e it changes its momentum.

so here momentum is not coserved.

c)this is also is not isolated system because friction (or you can say opposite force provided by the ocean no the ship) between ocean and ship gives the external forces thats changes the momentum of the system.

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