1. The problem statement, all variables and given/known data A 18.00 Kg lead sphere is hanging from a hook by a thin wire 3.80 m long, and is free to swing in a complete circle. Suddenly it is struck horizontally by a 4.50kg steel dart that embeds itself in the lead sphere. a)What must be the minimum initial speed of the dart so that the combination makes a complete circular loop after the collision 2. Relevant equations v1=(ms+md/md)v2 3. The attempt at a solution d=dart s=sphere mdvd=(ms+md)v2 vd=(ms+md/md)v2 v2 makes a complete circular loop so 1/2(md+ms)v22=(md+ms)2gr v2=sqrt(4gr) vd=(ms+md/md)sqrt(4gr) vd=(18+4.5/4.5)sqrt(4*9.8*3.8) =5*12.204=61.02m/s vd=61.02m/s Now my problem with this is the TA said I took all the right steps to solve this equation but I'm still getting an error using masteringphysics and I have gone over my work for errors 10 times by now. Is the work I did correct or am I missing something in my calculations. Thanks in advanced for any assistance.