Question

Определить мощность, развиваемую двигателем автомобиля, если на каждый километр пути при скорости 72 км/ч расходуется 74 г бензина. КПД двигателя 30%

Answer 1

N=A/t
Q=0.074*40800000=74*40800=3019200дж
Е=A=Q*n=30%*3019200=905760дж.
N=A/t=A/(s/v)=905760/(1000/20)=18115Ватт

Answer 2

Calculation of Engine Power

To determine the power developed by the engine of a car, we can use the formula:

Power = (Fuel consumption rate * Distance traveled) / Time

Given that the fuel consumption rate is 74 g/km, the distance traveled is 1 km, and the speed is 72 km/h, we can calculate the time taken to travel 1 km:

Time = Distance / Speed = 1 km / 72 km/h

Now, we can calculate the power developed by the engine using the formula mentioned above:

Power = (74 g/km * 1 km) / (1 km / 72 km/h)

To simplify the calculation, we convert the speed from km/h to m/s:

Speed = 72 km/h * (1000 m/km) / (3600 s/h) = 20 m/s

Substituting the values into the formula:

Power = (74 g/km * 1 km) / (1 km / 20 m/s) = 74 g * 20 m/s = 1480 g*m/s

To convert the power from grams multiplied by meters per second to watts, we need to divide by the conversion factor:

1 g*m/s = 0.00981 watts

Therefore, the power developed by the engine is:

Power = 1480 g*m/s * 0.00981 watts/g*m/s = 14.51 watts

However, we also need to take into account the efficiency (η) of the engine, which is given as 30%. The efficiency is defined as the ratio of useful output energy to the input energy. In this case, the useful output energy is the power developed by the engine, and the input energy is the energy contained in the fuel.

To calculate the actual power output of the engine, we need to divide the calculated power by the efficiency:

Actual Power = Power / Efficiency = 14.51 watts / 0.30 = 48.37 watts

Therefore, the actual power developed by the engine of the car is approximately 48.37 watts.