Question

Скутер едет со скоростью 27 км/ч. За 87 км пути он расходует 0,9 кг бензина. Определи полезную мощность двигателя, если КПД двигателя скутера равен 20 %. (Удельная теплота сгорания бензина q=46МДж/кг). ПРОМЕЖУТОЧНЫЙ И КОНЕЧНЫЙ ОТВЕТ ОКРУГЛИ ДО ДЕСЯТЫХ

Answer 1

Ответ: 0,714кВт

Объяснение:

Дано:

V=27км/ч

S=87км

m=0,9кг

η=20%=0,2

q=46МДж

============

Nпол-?

Теплота от сгорания бензина равна:

Q=q*m=46*0,9=41,4МДж

Полезная работа равна:

A=Q*η=41,4*0,2=8,28МДж

Время, за которое сделана полезная работа, равно:

t=S/V=87/27=3,22ч=11592с

Мощность двигателя равна:

N=A/t=8,28/11592=7,143*10⁻4МВт=0,714кВт

Answer 2

Calculation of Useful Power of the Scooter's Engine

To determine the useful power of the scooter's engine, we need to use the formula for power:

Power (P) = Work (W) / Time (t)

The work done by the engine can be calculated using the formula:

Work (W) = Force (F) x Distance (d)

In this case, the force can be calculated using the formula:

Force (F) = Mass (m) x Acceleration (a)

Since the scooter is moving at a constant speed, the acceleration is zero. Therefore, the force exerted by the engine is also zero. Hence, the work done by the engine is zero.

Now, let's calculate the time taken to cover the given distance of 87 km:

Time (t) = Distance (d) / Speed (v)

Substituting the given values:

Time (t) = 87 km / 27 km/h

Converting the distance and speed to SI units:

Time (t) = 87,000 m / 7.5 m/s

Calculating the time:

Time (t) = 11,600 s

Since the work done by the engine is zero, the useful power of the engine can be calculated as:

Useful Power (P) = Work (W) / Time (t) = 0 / 11,600 s = 0 W

Therefore, the useful power of the scooter's engine is 0 W.

Calculation of Fuel Efficiency

To calculate the fuel efficiency of the scooter, we need to determine the energy consumed by the engine. The energy consumed can be calculated using the formula:

Energy (E) = Fuel Consumption (m) x Specific Heat of Combustion (q)

Given that the fuel consumption is 0.9 kg and the specific heat of combustion is 46 MJ/kg, we can calculate the energy consumed:

Energy (E) = 0.9 kg x 46 MJ/kg

Converting the energy to SI units:

Energy (E) = 0.9 kg x 46,000,000 J/kg

Calculating the energy consumed:

Energy (E) = 41,400,000 J

Now, let's calculate the fuel efficiency, which is the ratio of the distance traveled to the energy consumed:

Fuel Efficiency = Distance (d) / Energy (E)

Substituting the given values:

Fuel Efficiency = 87 km / 41,400,000 J

Converting the distance to SI units:

Fuel Efficiency = 87,000 m / 41,400,000 J

Calculating the fuel efficiency:

Fuel Efficiency = 0.0021 m/J

Therefore, the fuel efficiency of the scooter is 0.0021 m/J.

Please note that the useful power of the engine is zero because the scooter is moving at a constant speed, and no work is being done against external forces.