Question

Автомобиль массой 4 т движется по горизонтальному участку дороги. При скорости 20 м/с отключают двигатель. Какую работу совершит сила трения до полной остановки автомобиля?

Answer 1

Сумма всех сил: ma=Fтр

Работа силы трения:   А=Fтр*S ; S-путь пройденный авт. до полной остановки.

А=m*a*S                                     S=(V^{2}-V_{0}^{2})/(2*a)

Подставляя S в формулу для работы получим:

A=m*a*V_{0}^{2}/(2*a)=4000*20^{2}/2=800000Дж

Answer 2

Calculation of Work Done by Friction

To calculate the work done by the force of friction to bring the car to a complete stop, we need to consider the initial velocity of the car, the mass of the car, and the distance traveled until it comes to a stop.

Given: - Mass of the car = 4,000 kg- Initial velocity of the car = 20 m/s To find the work done by the force of friction, we can use the work-energy principle, which states that the work done on an object is equal to the change in its kinetic energy.

The work done by the force of friction can be calculated using the formula:

Work = Force × Distance

In this case, the force is the force of friction, and the distance is the distance traveled until the car comes to a stop.

To find the force of friction, we can use Newton's second law of motion, which states that the force acting on an object is equal to the product of its mass and acceleration.

The acceleration of the car can be calculated using the equation:

Acceleration = (Final Velocity - Initial Velocity) / Time

Since the car comes to a stop, the final velocity is 0 m/s.

Now, let's calculate the force of friction and the work done by it.

Calculation Steps:

Step 1: Calculate the acceleration of the car. - Final velocity = 0 m/s - Time = ? - Acceleration = (Final Velocity - Initial Velocity) / Time

Since the car comes to a stop, the final velocity is 0 m/s. Therefore, the acceleration can be calculated as follows:

Acceleration = (0 m/s - 20 m/s) / Time

Step 2: Calculate the force of friction. - Mass of the car = 4,000 kg- Acceleration = ? - Force of friction = Mass × Acceleration

Step 3: Calculate the distance traveled until the car comes to a stop. - Distance = ? - Distance = (Initial Velocity × Time) + (1/2 × Acceleration × Time^2)

Step 4: Calculate the work done by the force of friction. - Work = Force of friction × Distance

Let's calculate the values step by step.

Step 1: Calculate the acceleration of the car:

Acceleration = (0 m/s - 20 m/s) / Time

Since the time is not given, we cannot calculate the exact value of acceleration.

Step 2: Calculate the force of friction:

Force of friction = Mass × Acceleration

Since the acceleration is not known, we cannot calculate the exact value of the force of friction.

Step 3: Calculate the distance traveled until the car comes to a stop:

Distance = (Initial Velocity × Time) + (1/2 × Acceleration × Time^2)

Since the time is not given, we cannot calculate the exact value of the distance traveled.

Step 4: Calculate the work done by the force of friction:

Work = Force of friction × Distance

Since the force of friction and the distance traveled are not known, we cannot calculate the exact value of the work done by the force of friction.

In conclusion, without the values of time, acceleration, force of friction, and distance traveled, we cannot calculate the exact work done by the force of friction to bring the car to a complete stop.