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**markosheehan** a smooth sphere of A of mass km moving with speed u collides directly with a smooth sphere B of mass m moving in the same direction with speed ku. A is brought to rest by the collision. find the speed of B after the collision in terms of k and u and prove k is greater or equal to 1/3

i can do the first part but not the second. using the conservation of momentum formula km(u)+m(ku)=m(v1)+km(0) so uk+ku=v1 2ku=v1

using the coefficient of restitution formula 0-u/2ku-ku=-e this doesnt seem to help