1. The problem statement, all variables and given/known data Calculate the centripetal acceleration module in the following cases as a multiple of g = 9.8 m / s ^ 2. a) a car traveling at 100km / h on a curve of radius 50m. b) a jet plane flying at 1,500 km / h and making a turning radius of 5km. c) a stone that is rotated every 0.5 s after a string of length 1 m d) a speck of dust on the edge of a disk of 30 cm diameter rotating at 33.33333 ... rev / min. e) a molecule in a centrifugal radius of 15cm rotating at 30,000 rev / min. 2. Relevant equations a) g= 9.8 m/s2 ar = v2/r ar = ug u: coefficient of friction(WHERE DO I GET THIS?!) haven't touched b) and on yet.. 3. The attempt at a solution so heres how i began... converted: vi = 100km/h = 10 000m/3600s = 27,78m/s ar= 1002/50 = 200 m/s2 ar = 9,8u Okay... so how do i get the coefficient of friction(u) if im not given any mass value?