1. The problem statement, all variables and given/known data What is the tension in the strap which the boy uses to hold onto the pack? Mass of Boy=45kg Mass of Pack=25kg θ=42° Coefficient of kinetic friction between boy and incline=0.35 Coefficient of kinetic friction between pack and incline=0.48 Acceleration of boy=4m/s^2 2. Relevant equations Fnet=F1+F2+F3...+Fn F=ma 3. The attempt at a solution Mass of boy=M Mass of pack=m Fpb=parallel force of boy etc... Fpb=Mgsinθ Fpp=mgsinθ fsb=0.35Mcosθ fsp=0.48mcosθ a(M+m)=Fpb+Fpp-fsb-fsp-T I'm really confused as to how to solve this since both acceleration and tension are unknowns. I've tried doing a lot of things to try and get a value for acceleration but none of them have given me the correct answer which is T=15N.