Jawabanmu

2014-04-03T20:50:26+07:00
V  = s/t
    = 20/4
    = 5 m/s
2014-04-03T20:58:51+07:00
F= n/t = 20/4 = 5 v= £amda * f = 20 * 5 = 100 ms-1