Question

В двух неподвижных лодках находятся мальчики. Масса первой лодки с мальчиком составляет 120 кг, второй-80кг. После того как мальчик на второй лодке оттолкнул от себя первую лодку, его лодка приобрела скорость, равную 1,5 м/с. Какую скорость приобрела первая лодка?

Answer 1

Дано:
m1=120кг
m2=80 кг
v2=1.5м/с
v1-?
Решение:
120/80=1.5
1.5/1.5=1 м/с
Ответ:v1=1м/с

Answer 2

Problem Analysis

We have two stationary boats with boys on them. The mass of the first boat with the boy is 120 kg, and the mass of the second boat is 80 kg. After the boy on the second boat pushes away from the first boat, the second boat acquires a velocity of 1.5 m/s. We need to find the velocity acquired by the first boat.

Solution

To solve this problem, we can use the principle of conservation of momentum. According to this principle, the total momentum before the interaction is equal to the total momentum after the interaction.

The momentum of an object is given by the product of its mass and velocity. Therefore, the momentum of the first boat before the interaction is equal to the momentum of the first boat after the interaction, and the momentum of the second boat before the interaction is equal to the momentum of the second boat after the interaction.

Let's denote the velocity acquired by the first boat as v1 and the velocity acquired by the second boat as v2.

The momentum of the first boat before the interaction is given by: Momentum1_before = mass1 * 0 (since the first boat is stationary)

The momentum of the first boat after the interaction is given by: Momentum1_after = mass1 * v1

The momentum of the second boat before the interaction is given by: Momentum2_before = mass2 * 0 (since the second boat is stationary)

The momentum of the second boat after the interaction is given by: Momentum2_after = mass2 * v2

According to the principle of conservation of momentum, we have: Momentum1_before + Momentum2_before = Momentum1_after + Momentum2_after

Substituting the values, we get: 0 + 0 = mass1 * v1 + mass2 * v2

Since the mass of the first boat is 120 kg and the mass of the second boat is 80 kg, we have: 0 = 120 * v1 + 80 * v2

We are given that the velocity acquired by the second boat is 1.5 m/s. Substituting this value, we get: 0 = 120 * v1 + 80 * 1.5

Simplifying the equation, we find: 0 = 120 * v1 + 120

Solving for v1, we get: v1 = -120 / 120 = -1 m/s

Therefore, the first boat acquires a velocity of -1 m/s.

Note: The negative sign indicates that the first boat moves in the opposite direction to the second boat.

Conclusion