Question

3 cases where kinetic energy become potential energy

Answer 1

--  Toss a rock straight up.  The kinetic energy you give it
with your hand becomes potential energy as it rises. 
Eventually, when its kinetic energy is completely changed
to potential energy, it stops rising.

--  When you're riding your bike and going really fast, you come
to the bottom of a hill.  You stop pedaling, and coast up the hill.
As your kinetic energy changes to potential energy, you coast
slower and slower.  Eventually, your energy is all potential, and
you stop coasting.

--  A little kid on a swing at the park.  The swing is going really fast
at the bottom of the arc, and then it starts rising.  As it rises, the
kinetic energy changes into potential energy, more and more as it
swings higher and higher.  Eventually it reaches a point where its
energy is all potential; then it stops rising, and begins falling again.

Answer 2

Some things that you could say are: 1. When a parked lorry starts to move; 2. When a stone is dropped from a building; 3. When a marathon runner starts to run.