Jawabanmu

2014-01-30T19:12:35+07:00
Cari dulu kecepatannya,
s=0,5 km = 500 m
t = 20 menit = 1200 s
V= \frac{s}{t}
V=  \frac{500}{1200}
V= \frac{5}{12}

E. kinetik =  \frac{1}{2} m v²
=  \frac{1}{2} . ( 45 ) . (  \frac{5}{12}
=  \frac{1}{2} . (45) .  \frac{25}{144}
=  \frac{1125}{288}
= 3,906
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