If the coefficient of kinetic friction between tires and dry pavement is 0.800, what is the shortest distance in which an automobile can be stopped by locking the brakes when traveling at 25.6m/s ?

Answer 1

Wext = KEfinal - KEinitial
f*s = 1/2mVfinal^2 - 1/2 mVinitial ^2
umg*s = 1/2m (Vfinal^2 - Vinitial ^2)

the mass can be cancel and Vfinal is zero since it will stop. So the displacmennt is given by

s = 1/2(Vinitial^2)/u*g