James Stewart, 2002 Motorcross/Supercross Rookie of the Year, is leading a race when he runs out of gas near the finish line. He is moving at 16 m/s when he enters a section of the course covered with sand where the effective coefficient of friction is 0.90. Will he be able to coast through this 15-m-long section to the finish line at the end? If yes, What is his speed at the finish line?
We are given the coefficient of friction which is: Cf = 0.90 The acceleration based on this would be: a = -Cf * g a = -0.90 * (9.81 m/s^2) a = -8.83 m/s^2 Calculate the distance at his total stop v = 0 using the formula: v^2 = vo^2 + 2ad where v is final velocity = 0, vo is initial velocity = 16, d is distance 0 = 16^2 + 2 (-8.83) d d = 14.5 m So he is short by 0.5 m, he does not reach the finish line
