Answer:
The boy with more mass will apply more momentum.
Explanation:
You see the boy with more mass which is the first boy with 70kg will apply more momentum.
The formula for momentum is P=mv.
In the first case,
P=70x4=280kgms-1
In second case,
P=50x4=200kgms-1
From this it is clear that the boat will go down to the side where the heavy boy is standing.
I hope this is clear for you.
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