[填空题]
A 2.30-m-long pole is balanced ve(l 41tbup16del+gitn rtically on its tip. It staro3jd fv/y4 lh ukdx-32ts to fall and its lower end does not slip. What will be the speed of the upper end of the pole just before it hits the ground? [Hint: Use conservation of energy.] k4udd/vf y2xjl-33 oh $m/s$