Back, Height
You fly north to the moon and break your back when you finally land on it. You weren’t braced for impact so when you hit the moon, your back took all of the impact.
Imagine flying north to the moon. Feel the force of being rocketed through space on your journey. Now feel your spine telescope and your back break. It really hurts.
はい
せ, そむ
None
Your back hurts so much that the only way to properly explain the pain is in haiku (はい) form. I flew to the moon. It is there I broke my back. My back hurts real bad.
Say this haiku out loud. Memorize it and use this haiku to remember this kanji.