- #1

- 30

- 0

## Homework Statement

If a curve with a radius of 60m is properly banked for a car travelling at 60km/h (16.66m/s) with no friction, what must be the coefficient of friction if the car is not to skid when travelling at 90km/h (25m/s)

## Homework Equations

mac = mv^2/r

## The Attempt at a Solution

The answer is 0.39

First we need to find the angle, so since it said that when the speed was 60km/h, there is No friction, we can make this equation.. and do the following calculations

Fgx = mac

mgsinɵ = mv^2/r

gsinɵ = v^2/r

9.8sinɵ = 16.66^2/60

sinɵ = 4.625/9.8

ɵ = 28.16

So now we have the angle..

We can now use the speed 90km/h with our new angle.

So the new equation is..

Ff + Fgx = mv^2/r

μFn + Fgx = mv^2/r

μmgcos28 + mgsin28 = mv^2/r

μ9.8cos28 + 9.8sin28 = (25)^2/60

μ(8.65) + 4.6 = 10.41

μ = 10.41 - 4.6/8.65

μ = 0.67

So I'm not sure where I went wrong..

the answer is 0.39 :O