р керосина = 800кг/м3 ))
mg*cosk-Fтр=ma
mg*cosk-μmg*sink=ma
g(cosk-μ*sink)=a
s=at^2/2
2s/t^2=g(cosk-μ*sink)
t=√(2s/g(cosk-μ*sink) =1.7c