Jawabanmu

2014-08-24T19:37:55+07:00
72km/jam = 72000m/3600s = 20m/s
vt = v0 + a.t
20 = 0 + a.30
20 = 30a
a = 20/30 = 2/3 m/s²
2014-08-24T19:39:07+07:00