1. The problem statement, all variables and given/known data A small block of mass "m" slides on a frictionless horizontal surface as it travels inside of a hoop of radius "R". The coefficient of friction between the block and the wall is "u", therefore, the speed of the block decreases. In terms of "m", "R", "u", and "v" (the block's velocity), find expressions for the following. 1. The frictional force on the block: (I believe it is f = (v^(2) * m / R) 2. The block's tangential acceleration (dv/dt). I really need this one. 3. Use the equation from #2 to find the time required to reduce the speed of the block to one-third of its original velocity from its original velocity. 2. Relevant equations N/A 3. The attempt at a solution #1 should be "f = (v^(2) * m / R" #2 All I have so far is #1 solved for "v". "v = sqrt(f * R / m)" #3 Once I have #2, this will be cake.