KE = half of mass times squared speed
18 = 0.5 * mass * (3m/s)^2
18 = 4.5 mass
mass = 18 / 4.5 = 4 kg
100 meters in 9.92 seconds,
=distance/time
=100m/9.92s
=10.0806 m/s
Momentum, p = m.v
m of the girl = 60.0 kg
m of the boat = 180 kg
v of the girl = 4.0 m/s
A) Momentum of the girl as she is diving:
p = m.v = 60.0 kg * 4.0 m/s = 24.0 N/s
B) momentum of the raft = - momentum of the girl = -24.0 N/s
C) speed of the raft
p = m.v ; v = p/m = 24.0N/s / 180 kg = -0.13 m/s [i.e. in the opposite direction of the girl's velocity]
