Jawabanmu

2014-08-20T17:28:39+07:00
Dik :
l = 2 m 
m = 25 gram ==> 25.10^-3 kg
v = 40 m/s
F = ... ?

v = √F.l/m
40 = √F.2/25.10^-3
(40 = √F.2/25.10^-3)^2
1600 = F.2/25.10^-3
1600x25.10^-3 = 2F
40 = 2F
F = 40/2
F = 20 N
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