Jawabanmu

2014-01-26T20:47:13+07:00
Pkai rumus
vt^2=2.g.h
vt= \sqrt{2gh}
vt= \sqrt{2.10.20}
vt=20

slanjutnya cri waktu
vt=gt
t=vt/g
t=20/10
t= 2s