[填空题]
A 2.30-m-long pole is balanced vertically on its tip. It starts lm 04d6xwu9a;s )*near t4xjh to fall andxvbb, ozq(ew6 r(y/0 d its lower end does not slip. What will be the speed of the upper /(b, w0 boq(yz6rvdxeend of the pole just before it hits the ground? [Hint: Use conservation of energy.] $m/s$