The hammerhead on the pole has an actual weight of 15 pounds. So by itself, it's not too heavy. But fitted to the pole, it's equal to ten times that.
15 seconds sound clip from the Frozen movie soundboard.
You can hear this line at 00:54:02 in the DVD version of the movie.
Quote context
[...]
- Leave. Go onto the next chamber now.
- Teacher, I came to learn to fight, but this...
- Don't you underestimate this phase.
- How are your wrists? Are they real strong?
- Now move your grip at least two feet.
- Ready?
(WOODEND DRUM AND GONG, MONKS CHANTING)
[...]