1. The problem statement, all variables and given/known dat So a child is running with the conveyer belt. Relative to the conveyer belt he is running 2.5 m/s. 2. Relevant equations To find the relative velocity of the child to earth, I'm guesing is: Velocity of child relative to earth= (v of belt to earth)+(v of child to belt) If V child-belt = 2.5, that means he is running 2.5 m/s while on the belt right? So if the child is running against the belt at the same speed, is the equation the same? Is the V child-belt still 2.5 but in the opposite direction? If i plug in random numbers in the equation for running against the belt, it seems to work still. Say belt is moving 1m/s --> -1.5 m/s= 1 m/s - 2.5 m/s, seems right, he runs -1.5 relative to stationary observers. But I would assume, since the belt is coming towards the child, the relative velocity of the child to the belt would be greater than 2.5 m/s? and would equal |Velocity of conveyer belt to earth| + |Velocity of child running (not sure what reference frame now)|?