when i was ten years old and my sister six me and her often went to the park to play as kids do. the swings were our favorite since they went the fastest after. the swings work by increasing your momentum back and forth by kicking your legs and increasing energy within the swings constantly until it reaches a comfortable level for the person in the swing. at either highest point of the swing the potential energy reaches its peak and many children including my sister and i t the time like to jump off of the swing. one day i decided to do just that and as my potential energy changed to kinetic i bent my knees slightly to allow the momentum to stop slower. my sister on the other hand landed on her elbow and broke her arm. one trip to the hospital later and around 4 months of wearing a cast we where right back on the swing set.