Minimum coefficient of static friction

AI Thread Summary
To determine the minimum coefficient of static friction on a 19-degree incline, the correct approach involves using the tangent function. The user initially calculated the normal force and static friction incorrectly, leading to an erroneous answer of 0.15. It was pointed out that the gravitational acceleration (9.8 m/s²) should not be included in the coefficient calculation. The correct calculation involves simply using the tangent of the angle, tan(19), without additional factors. The discussion emphasizes the importance of ensuring the calculator is set to the correct mode for angle measurement.
emily081715
Messages
208
Reaction score
4

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


IMG_7745.JPG
 
Physics news on Phys.org
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
 
emily081715 said:
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.
 
haruspex said:
Degrees versus radians.
i don't understand?
 
emily081715 said:
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.
 
haruspex said:
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.
 
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?
 
emily081715 said:
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 said:
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
 
  • #10
emily081715 said:
well actually i know its incorrect
so just tan (19)
 
  • #11
emily081715 said:
so just tan (19)
Yes.
 
Back
Top