This is a Name That Trauma. I was watching a kid's show in the mid to late '70s. I have always believed it to be SESAME STREET, but it is possible it was THE ELECTRIC COMPANY.
It was a short cartoon clip and the only part that stuck in my mind was that it involved a blonde kid imagining what would happen if he fell off of a building or a mountain. It showed him at the bottom after his tumble, and from what I remember, his arms, legs AND head were not attached to his torso anymore!
I was always a little on edge and ready to run when I watched this show after this. I NEVER knew when it would spring up again.