1. The problem statement, all variables and given/known data To explain the forces at work when a marble is released from a height and then eventually comes to rest. We did this experiment where two lengths of hose pipe were taped together. The hosepipe was then bent into a semicircular shape (forming a track) and secured onto a clamp stand. We then had to release marbles from varying distances from the bottom of the hose pipe ramp and measure the time taken for the marble to come to rest. 2. Relevant equations 3. The attempt at a solution I know the marble has GPE equal to mgh when released and picks up KE as it rolls down the track. I am struggling to apply some rigorous physics as to why it stops. Air resistance is an obvious one. The marble seems to grip the track so I would argue the friction is static friction. If there is no kinetic friction then am I correct in saying friction doesn't oppose the motion of the marble? Is the main opposing force the bumpiness of the hose pipe so the marble encounters a large number of small collision and each collision provides an opposing force to slow down the marble?