1. The problem statement, all variables and given/known data A uniform marble rolls down a symmetric bowl, starting from rest at the top of the left side. The top of each side is a distance h above the bottom of the bowl. The left half of the bowl is rough enough to cause the marble to roll without slipping, but the right half has no friction because it is coated with oil. (a) How far up the smooth side will the marble go, measured vertically from the bottom? 2. Relevant equations Conservation of energy 3. The attempt at a solution While applying conservation of energy, why we should not consider the work done by the friction force on the marble? Kindly explain me.