1. The problem statement, all variables and given/known data http://www.physics.ohio-state.edu/undergrad/greStuff/Problems_2009/Mechanics_4.pdf exercise 83 2. Relevant equations Conservation of energy?!! 3. The attempt at a solution Well what I think is that if there is no friction, whenever the initial velocity is >0, the particle will just keep sliding over all the bumps, right? The potential energy will just be transformed into kinetical and vice versa ...or am I terribly missing something? The explanation is here: http://www.physics.ohio-state.edu/undergrad/greStuff/Solutions_2009/Mechanics_4.pdf but it seems really twisted to me.