Exercise 1 solution

Typical result: under steady pull the bowline holds its loop and keeps its size. When the rope is slack and shaken or flexed, the knot can loosen and the loop may start to slip, especially in slippery synthetic cord.
A stopper (for example an overhand) tied in the tail, or simply a longer tail, makes it much less likely to work loose.
Results vary with the cord; stiff rough cord grips better than slippery cord.