Jawaban:

m = 20g = 0,02 kg

m₂ = 5kg

θ = 60⁰

L = 2m

cos 60 = (L - h) / L

cos 60 = (2 - h) / 2

0,5*2 = 2-h

h = 2-1 = 1m

kekekalan momentum sebelum vs sesudah tumbukan

m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'

v₂ = 0

v₁' + v₂' = v'

0,02*v₁ = (m₁ + m₂)v'

0,02*v₁ = (0,02 + 5)v'

0,02*v₁ = 5,02v'    pers 1

Ep = Ek

mgh = ½mv'²

2gh = v'²

2*10*1 = v'²

v'² = 20

v' = 4,47 m/s

0,02*v₁ = 5,02v'

v₁ = 1121,97 m/s

Ek =  ½mv² = ½ 0,02*1122² = 12589 J  

1. h = 1 m   benar

2. v' = 4,47 m/s  benar

3. v₁ = 1121,97 = 1122 m/s  benar

4. Ek = 12589 J   salah

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