jawblah pakai cara nomor 10

lengan beban = 2m
panjang tuas = 4m
lengan kuasa = 4m - 2m = 2m
berat baban = 400N

F = w × lk / lb
= 400N × 2m / 2m
= 400N

Fk x lk = Fb x lb
Fk x (4-2) = 400 x 2
Fk x 2 = 800
Fk = 800/2
Fk = 400N

keterangan:
Fk = gaya kuasa
lk = lengan kuasa
Fb = gaya beban
lb = lengan beban

*semoga membantu. sukses selalu ^_^