[填空题]
A 2.30-m-long pole i1ycu- ,e 0-rnvqan5bzajfo /;s :owg(s 6(qpc abalanced vertically on its tip. It starts to fall and its lower end does not slip. What will be the speed of the upper end of the pole just before it 6(wag:cps q (ohits the ground? [Hint: Use conservation of energy.] $m/s$