Posted by kelly on .
You have a mass of 71 kg and are on a 51degree slope hanging on to a cord with a breaking strength of 165 newtons. What must be the coefficient of static friction to 2 decimal places between you and the surface for you to be saved from the fire?
In the previous problem if the coefficient of static friction is zero, to the nearest tenth of a degree, what would the incline angle have to be in order for the cord not to break?

physics 
Elena,
x: 0= m•g•sinαTF(fr),
y: 0 =  m•g•cos α +N.
F(fr) =k•N=k• m•g•cos α,
F(fr) = m•g•sinα – T,
k• m•g•cos α = m•g•sinα – T,
k= tan α – T/m•g•cos α =
=tan51º 165/71•9.8•cos51 =
= 0.86.
If k=0,
tan α = T/m•g•cos α,
sin α/ cos α = T/m•g•cos α,
sin α = T/m•g =167/71•9.8 =0.24
α =13.88º