1. The problem statement, all variables and given/known data To meet a U.S. Postal Service requirement, footwear must have a coefficient of static friction of 0.500 or more on a specified tile surface. A typical athletic shoe has a coefficient of 0.755. In an emergency, what is the minimum time interval in which a person starting from rest can move 3.45 m on a tile surface if she is wearing the following footwear? (a) footwear meeting the Postal Service minimum (b) a typical athletic shoe 2. Relevant equations Fs[tex]\leq[/tex] (less than or equal to) [tex]\mu[/tex]sn (static frictional constant times the vertical force of the object) Fk=[tex]\mu[/tex]kn (kinetic frictional force times the vertical force of the object [tex]\sum[/tex] F = ma 3. The attempt at a solution I don't even know how to start this problem... suppose I use n=1 as the weight of the runner/person... I would get F=0.5N for the force needed to over come to static frictional force of the U.S Postal Service shoes.. but how do I use that to calculate the time?