See the attachment Q5
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?