The coefficient of static friction between the 2.3 kg crate and the 35.0° incline of Figure P4.47 is 0.241. What minimum force, F, must be applied to the crate perpendicular to the incline to prevent the crate from sliding down the incline?

Answer 1

ΣF(x) = 0: m•g•sinα=F(fr)
ΣF(y) = 0: m•g•cosα +F = N
F(fr)=μ•N= μ• (m•g•cosα +F)
m•g•sinα= μ• (m•g•cosα +F)
F=(m•g/μ) •(sinα -μ• cosα)