1. The problem statement, all variables and given/known data A symmetric block of mass M1 with a groove of hemisphere shape of radius R rests on a smooth horizontal surface in contact with the wall as shown in the figure. A small block of mass m2 slides without friction from the initial position .Find the maximum velocity of the block M1.Describe the motion of both the blocks M1 and m2. ( M1=100 Kg m2=10kg R=5m g=10m/s2). 2. Relevant equations 3. The attempt at a solution Initially m2 is is at 1 and slides down to 2 .Since M1 has a wall towards its left side ,the wall exerts a force on M1 till m2 reaches 2 because m2 pushes against M1.So momentum of two block system can not conserved till m2 reaches 2.Afterwards , momentum can be conserved taking initial momentum when m2 is at 2. Velocity of m2 at 2 can b found using conservation of energy between points 1 and 2. Loss of potential energy = Gain in Kinetic energy velocity of m2 at 2 = 10m/s Now I have a doubt here when block m2 moves from 2 to 3....If we consider only m2 then kinetic energy of m2 at 2 should completely convert in Potential energy at 3 which gives the height to which the block rises i.e R. This means block m2 moves back and forth between 1 and 3. But if conservation of momentum is applied then as block m2 moves from 2 to 3 the block M1 also moves ie when m2 reaches 3 then M1 is moving and m2 is at rest w.r.t M1 Applying conservation of energy Loss in Kinetic energy of m2 =Gain in potential energy of m2 + gain in kinetic energy of (M1+m2). This gives height to which block m2 rises less than R . Why two different results... Where am I getting it wrong?