[填空题]
A 2.30-m-long pole is balanced vera hl;9e-qs 4h2hp t8pbtically on its tip. It starts 8 1jh *dxnjas29;dsedto 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 conservaj9xn;* ad2dssd1ej 8htion of energy.] $m/s$