Question

4. Автомобиль массой 2Т, движущийся со скоростью 20 м / с, после выключения двигателя тормозит и останавливается. Чему равно время торможения, если сила сопротивления равна 40кН?

Answer 1

Ответ:1 s

Объяснение:

F= 40 kN = 4 ×10^4

v0 = 20m/c

m = 2 × 10^3 kg

F=ma

a = F/m= 20

v0-v = at

V= 0

t = v0/a=20/20 = 1 s

Answer 2

Calculation of Braking Time

To calculate the braking time of a car, we need to consider the force of resistance acting on the car. In this case, the force of resistance is given as 40 kN.

The force of resistance can be calculated using Newton's second law of motion, which states that force is equal to mass multiplied by acceleration. In this case, the acceleration is the deceleration of the car when it is braking.

The formula to calculate the force of resistance is:

Force of Resistance = Mass x Deceleration

Given that the mass of the car is 2 tons (or 2000 kg) and the force of resistance is 40 kN, we can rearrange the formula to solve for the deceleration:

Deceleration = Force of Resistance / Mass

Substituting the given values:

Deceleration = 40,000 N / 2000 kg

Now we can calculate the deceleration:

Deceleration = 20 m/s^2

The deceleration represents the rate at which the car slows down.

To calculate the braking time, we need to use the equation of motion:

Final Velocity = Initial Velocity + (Acceleration x Time)

In this case, the initial velocity is 20 m/s (given), the final velocity is 0 m/s (since the car comes to a stop), and the acceleration is -20 m/s^2 (negative because it represents deceleration).

Rearranging the equation to solve for time:

Time = (Final Velocity - Initial Velocity) / Acceleration

Substituting the given values:

Time = (0 m/s - 20 m/s) / -20 m/s^2

Simplifying the equation:

Time = 1 second

Therefore, the braking time for the car is 1 second.