[填空题]
You stand at the top of a cliff while your friend stan-( *rkoe /qsqzds on oou.xi. gk1th)vy/4 a the ground below you. You drop a ball from rest and see that it takes 1.2 s for the ball to hit the ground below. Your friend then picks up the ball and throws it up to you, such thvtgy1hao io )x.u4/ .kat it just comes to rest in your hand. What is the speed with which your friend threw the ball? m/s
