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## Homework Statement

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.

## Homework Equations

a)

g= 9.8 m/s

^{2}

a

_{r}= v

^{2}/r

a

_{r}= ug

u: coefficient of friction(WHERE DO I GET THIS?!)

haven't touched b) and on yet..

## The Attempt at a Solution

so here's how i began...

converted:

v

_{i}= 100km/h = 10 000m/3600s = 27,78m/s

a

_{r}= 100

^{2}/50 = 200 m/s

^{2}

a

_{r}= 9,8u

Okay... so how do i get the coefficient of friction(u) if I am not given any mass value?