Minimum coefficient of static friction

[emily081715]

Homework Statement

If the incline of the driveway is 19 ∘ from the horizontal, what must the minimum coefficient of static friction be between your shoes and the ice?

Homework Equations

Fs=uN

The Attempt at a Solution

 

[emily081715]

i need help figuring out my error, i assumed that the N force was equal to mgcosθ and Fs was equal to mgsinθ. the masses must cancel out and following what is written on my paper, i got and answer of 0.15. this is incorrect and i need help finding out why

 

[haruspex]

i need help figuring out my error, i assumed that the N force was equal to mgcosθ and Fs was equal to mgsinθ. the masses must cancel out and following what is written on my paper, i got and answer of 0.15. this is incorrect and i need help finding out why

Degrees versus radians.

 

[emily081715]

Degrees versus radians.

i don't understand?

 

[haruspex]

i don't understand?

Did you plug the 19 degrees into the tan function of a calculator? It can probably be set to expect angles to be specified in degrees or radians, but you have to make sure you select the right one.

 

[emily081715]

Did you plug the 19 degrees into the tan function of a calculator? It can probably be set to expect angles to be specified in degrees or radians, but you have to make sure you select the right one.

 

[emily081715]

so my original answer was in my radians and i did 9.8 tan (19) in degrees and got 3.4 as the answer, is that to big?

 

[haruspex]

so my original answer was in my radians and i did 9.8 tan (19) in degrees and got 3.4 as the answer, is that to big?

Why the 9.8? g is not part of the coefficient.

 

[emily081715]

so my original answer was in my radians and i did 9.8 tan (19) in degrees and got 3.4 as the answer, is that to big?

well actually i know its incorrect

 

[emily081715]

well actually i know its incorrect

so just tan (19)

 

[haruspex]

so just tan (19)

Yes.