[填空题]
A stone is dropped fdu mru dbd 9nmo;0+coai 2r5s-y z8d53rom the vwz xbdx/g2e-m,):fy ju3( s droof of a building; 2.20 s after that, a second stone is thrown straight down with an initial spee3d) v wzb-x( emfu:x/,d js2gyd of $25 \; m/s$ and the two stones land at the same time. (a) How long did it take the first stone to reach the ground? $s$ (b) How high is the building? $m$ (c) What is the speed of the first stone just before it hit the ground? $m/s$ (d) What is the speed of the second stone just before it hit the ground? $m/s$
