- #1
McKeavey
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Homework Statement
If a curve with a radius of 60m is properly banked for a car traveling at 60km/h (16.66m/s) with no friction, what must be the coefficient of friction if the car is not to skid when traveling 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