Jawabanmu

2014-08-24T19:03:38+07:00
72km/jam = 72000m/3600sekon = 20 m/s
0.5 menit = .5 x 60 sekon = 30 sekon
a. s = s0 + v0.t + 1/2.a.t² = 0 + 20m/s.30s + 1/2.4.900 = 600 + 1800 = 2400 meter
b. vt² = v0² + 2.a.s = 20²m/s + 2.4.2400 = 400 + 19200 = √19600 = 140 m/s
   atau simple vt = v0 + a.t = 20 + 4.30 = 20+120 = 140 m/s