when a sailor jump out of a boat the boat is pushed backward explain why
Answers
Mass of the person = Mp mass of boat = Mb
Initially both are at rest - let us say. ( It does not matter even if the boat is moving with a uniform speed.)
Initial velocity of Person = Up = 0 initial velocity of boat = Ub = 0
Final Velocity of P = Vp Final velocity of boat = Vb
Suppose the person jumps from the boat with a considerably velocity Vp in the forward direction. Then let boat move by Vb velocity.
As conservation of momentum law says
Mp Up + Mb Ub = Mp Vp + Mb Vb
0 + 0 = Mp Vp + Mb Vb
Vb = - Mp Vp / Mb
So Vb is in the direction opposite to Vp. It may be small, as Mb > Mp.
Even if it is a ship, When a person jumps off, the ship moves backwards, if we do not consider other external factors. It may be a very small quantity.
It is the newtons third law that explains this phenomenon. The person exerts a force F on the boat while jumping off, with his foot. So the boat moves backwards. The force with which the man jumps, it comes from the normal reaction force F from the boat on the man. So both move in opposite directions with the force F given by the other.