1. The problem statement, all variables and given/known data A bicyclist makes a three quarter turn of radius 1.5 m at constant speed. During the turn, the only horizontal force acting on the bicyclist is a static friction force of constant magnitude 250 N. The total mass of the bicycle and rider is 60 kg. 2. Relevant equations 3. The attempt at a solution The path: http://www.mathgoodies.com/lessons/fractions/circles/circle_three_fourths_blue.gif The circle's radius = 1.5 The bicyclist's speed: 2.5 Acceleration at the point A: (-25/6,0) Velocity at the point A: (0, 2.5) Velocity at the point B (the final point of the journey): (2.5,0) And the average velocity (-0.53, -0.53) I have computed everything correctly except for average velocity and I have no idea how to get the right angle. I guessed there should be minus signs (-1.25, -1.25) but of course magnitudes are wrong. I realize that this is because of acceleration. You can't just reproduce strategies fit for linear motion, i.e. to divide the sum of final and initial velocity by two.