Jawabanmu

2014-06-08T20:31:10+07:00
Dik: m= 1 kg  h=20m h'=5m
h=s= h-h' = 20 m-5m = 15 m
 
a = g

s= 1/2.at² => t=√s : 1/2.a
t= √15: 1/2. 10 m/s²
t= √3

v= a.t = 10 m/s².√3 s = 10√3 m/s
 
Ek= 1/2.m.v²
= 1/2. 1 kg . (10√3 m/s)² 
= 1/2. 1 kg . 300 m²/s²
= 150 Joule