[填空题]
A 2.30-m-long pole is byg ;kory 5::fv v 4-tauyv69vzalanodqaxt v4w)+ k +tiv7; od .egg*5oq8jced vertically on its tip. It starts to fall and its lower end does not slip. What will be the speed of the upper end o+vjqk4vo7gd e xto8t;awq o5 +.) i*dgf the pole just before it hits the ground? [Hint: Use conservation of energy.] $m/s$