Cari dulu vB dengan Hukum Kekekalan Momentum
EMA = EMB
EPA + EKA = EPB + EKB
0 + 1/2 mvA^2 = mghB + 1/2 mvB^2
0 + 1/2 m(2√15)^2 = m10(1,5) + 1/2 mvB^2
(ruas kanan dan kiri dibagi m)
0 + 1/2(2√15)2 = 10(1,5) + 1/2 vB^2
0 + 1/2(60) = 15 + 1/2 vB^2
0 + 30 = 15 + 1/2 vB^2
30 - 15 = 1/2 vB^2
15 = 1/2vB^2
2(15) = vB^2
vB^2 = 30 m2/s2
Energi Mekanik di Posisi B
EMB = EPB + EKB
EMB = mghB + 1/2 mvB^2
EMB = m10(1,5) + 1/2 m(30)
EMB = 15m + 15m
EMB = 30m Joule
c. Posisi C: