Question

Лодка длиной 3м и массой 120кг стоит на спокойной воде. На носу и корме находятся два рыбака массами 60кг и 90кг. На сколько сдвинется лодка относительно воды, если рыбаки поменяются местами?

Answer 1

Найдем центр масс системы из равенства моментов сил
90(1,5-x)=120x+90(1.5+x)

когда рыбаки поменяются местами, центр масс системы останется на месте 
из симметрии лодка сместится на расстояние 2х
надеюсь уравнение сам решишь

Answer 2

Calculation of Boat Displacement

To calculate the displacement of the boat when the fishermen change places, we need to consider the conservation of momentum. The total momentum before and after the fishermen change places should be the same.

Let's denote the initial position of the boat as "A" and the final position after the fishermen change places as "B". The boat has a length of 3m and a mass of 120kg. There are two fishermen on the boat, one at the bow (nose) with a mass of 60kg and one at the stern (rear) with a mass of 90kg.

Before the fishermen change places, the total momentum of the system is given by the equation:

Total Momentum Before = Total Momentum After

The momentum of an object is calculated by multiplying its mass by its velocity. In this case, since the boat is initially at rest, the momentum of the boat is zero.

Let's assume that the fishermen change places instantaneously, without any external forces acting on the boat. In this case, the momentum of the fishermen will also be zero before and after the change.

Therefore, the equation can be simplified to:

0 = 0 + 0

This means that the total momentum of the system remains zero before and after the fishermen change places. As a result, the boat will not move relative to the water when the fishermen switch positions.

So, the answer to the question is that the boat will not move relative to the water when the fishermen change places.

Please let me know if you found this information helpful or if you have any further questions!