Question

Поезд массой 1200 т тормозит. Начальная скорость при торможении 72 км в час, тормозной путь 3 км. Найти работу силы трения? С решением пожалуйста Заранее благодарен

Answer 1

Дано m=1.2*10^6 кг     V0=20 м/с     V=0      Атр- ?

Атр= - m*Vo^2/2=-1.2*10^6*400/2=-240 МДж

Answer 2

Calculation of Frictional Force

To find the frictional force, we can use the equation:

Frictional Force = Mass * Acceleration

In this case, the mass of the train is given as 1200 tons, which is equivalent to 1,200,000 kilograms (since 1 ton = 1000 kilograms). The initial velocity of the train is 72 km/h, and the braking distance is 3 km.

To calculate the acceleration, we can use the equation:

Acceleration = (Final Velocity - Initial Velocity) / Time

Since the train is coming to a stop, the final velocity is 0 km/h. We can convert the velocities to m/s by dividing by 3.6 (since 1 km/h = 1000 m/3600 s).

Let's calculate the acceleration first:

Acceleration = (0 m/s - (72 km/h / 3.6)) / Time

The time can be calculated using the equation:

Time = Distance / Velocity

In this case, the distance is the braking distance of 3 km, and the velocity is the initial velocity of 72 km/h.

Time = 3 km / (72 km/h / 3.6)

Now, we can substitute the values into the equation for acceleration:

Acceleration = (0 m/s - (72 km/h / 3.6)) / (3 km / (72 km/h / 3.6))

Simplifying the equation:

Acceleration = (0 - 20) / (3 / 20) m/s^2

Acceleration = -400 / 3 m/s^2

Now, we can calculate the frictional force using the equation:

Frictional Force = Mass * Acceleration

Frictional Force = 1,200,000 kg * (-400 / 3) m/s^2

Calculating the frictional force:

Frictional Force = -160,000,000 / 3 Newtons

Therefore, the frictional force acting on the train during braking is approximately -53,333,333.33 Newtons.

Please note that the negative sign indicates that the force is acting in the opposite direction to the motion of the train.