A car drove 18 km at a constant speed on a straight highway. The speed of the car is shown in the figure. The engine power of the car is 50 kW, The size of the car's resistance, the work done by the car's engine

A car drove 18 km at a constant speed on a straight highway. The speed of the car is shown in the figure. The engine power of the car is 50 kW, The size of the car's resistance, the work done by the car's engine

From P = FV, we can get the traction force F = P / V, and the speed V is read out in the figure. Since you have not given the figure, please calculate it by yourself
Because the car is moving at a constant speed, then f = friction F
Engine work w = f * s s = 18000m
Then w can be obtained

A passenger car and a freight car drive from Shanghai to Nanjing at the same time. The passenger car runs 92 kilometers per hour and the freight car 85 kilometers per hour. How many hours later, the distance between the two cars is 21 kilometers
It's better not to set up equations. If you set up equations, you should have a detailed process and explanation. 3Q!

Distance difference = speed difference * time
Time = distance difference / speed difference
=21 / (92-85) = 4 (hours)