[填空题]
A stone is dropped from the roofiv lw2mi6z+ p, 93/e ) 4ojlz.1 :xqxrshifvsa of a high building. A s3dk j+4 vk)ll7 mcy:a)ry 8ilvecond stone is dropped 1.80 s later. How far apart are the stones w l)drv 4av38ylm:k ckjyi7l) +hen the second one has reached a speed of $24 \; m/s$? $m$