1. The problem statement, all variables and given/known data See the attachment Q5 2. Relevant equations 3. The attempt at a solution Let's begin with part (a) first. After finishing this homework (see the second attachment), I suddenly noticed 1 thing. The friction will gradually decrease to zero and then change the direction to become same as the motion direction. Therefore, my work on part (a) would be wrong. Since I assume the friction is a constant (mgμsinθ). How do I fix it? And also, is my way to find the minimum coeff of kinetic friction correct? And for part (b), it is really that easy?