Question

Автомобиль массой 5 т движется равномерно с горы с выключенным двигателем. Коэффициент трения равен 0,7. Угол наклона горы - 30 градусов. Чему равна сила трения (в кН)?

Answer 1

Автомобиль движется без ускорения. Сила трения

Fтр=kтр*N=kтр*m*g*cos(фи)

 

Fтр=0,7*5000*9,8*cos(30)=29700[Н]

Answer 2

Calculation of Frictional Force

To calculate the frictional force acting on the car, we need to consider the weight of the car and the angle of inclination of the hill. The formula for calculating the frictional force is:

Frictional force = coefficient of friction * normal force

The normal force is the component of the weight of the car perpendicular to the surface of the hill. It can be calculated using the formula:

Normal force = weight of the car * cos(angle of inclination)

Given: - Mass of the car = 5 t (tonnes) - Coefficient of friction = 0.7 - Angle of inclination of the hill = -30 degrees

First, let's convert the mass of the car from tonnes to kilograms: 1 t = 1000 kg So, the mass of the car is 5 t = 5000 kg.

Now, let's calculate the normal force: Normal force = weight of the car * cos(angle of inclination)

The weight of the car can be calculated using the formula: Weight = mass * gravitational acceleration

Assuming the gravitational acceleration is approximately 9.8 m/s^2, we can calculate the weight of the car: Weight = 5000 kg * 9.8 m/s^2

Now, we can calculate the normal force: Normal force = Weight * cos(-30 degrees)

To calculate the cosine of -30 degrees, we need to convert it to radians: -30 degrees = -30 * (pi/180) radians

Now, let's calculate the normal force using the given values and formulas.

Calculation Steps:

1. Convert the mass of the car from tonnes to kilograms: 5 t = 5000 kg. 2. Calculate the weight of the car: Weight = 5000 kg * 9.8 m/s^2. 3. Calculate the normal force: Normal force = Weight * cos(-30 * (pi/180)).

Let's perform the calculations.