Downstream velocity = still water velocity+current velocity

Countercurrent velocity = still water velocity-current velocity

Still water velocity = (downstream velocity+countercurrent velocity) ÷2

Water velocity = (downstream velocity-countercurrent velocity) ÷2

2. Formula for two ships sailing in opposite directions:

Downstream speed of ship A+downstream speed of ship B = still water speed of ship A+still water speed of ship B?

3. Formula for two ships sailing in the same direction:?

Hydrostatic speed of rear (front) ship-Hydrostatic speed of front (rear) ship = the speed of narrowing (expanding) the distance between two ships.

The speed of the ship is definitely greater than the speed of water, and the speed of the downstream is definitely greater than the speed of the upstream. ? So the ship speed is equal to (downstream speed+upstream speed) ÷2. The velocity of water is equal to (downstream velocity-countercurrent velocity) ÷2, and the result of adding the two velocities is large. Divided by 2 is the speed of the ship, and the result of subtracting the two speeds is very small. Divided by 2 is the speed of water.

Extended data

Related applications:

Port A and Port B are 720 kilometers apart. It takes 35 hours for a ship to travel back and forth between the two ports, and sailing against the current takes 5 hours more than sailing against the current. Sailing boats travel 24 kilometers per hour in still water, and it takes 64 hours for sailing boats to travel back and forth between the two ports.

Solve the sailing time between two ports, time = distance/speed. We know the distance, but the speed only knows the speed of the sailboat. We also need to calculate the speed of water flow. We can calculate the speed of water flow according to the round trip of the ship. It takes 35 hours to go back and forth, and the retrograde time is 5 hours longer than the forward one. We can find that the downstream time is 15 hours and the upstream time is 20 hours.

Further, the downstream speed = 720÷ 15 = 48km/ hour and the upstream speed = 720÷20 = 36km/ hour can be calculated, and then the outlet speed =(48-36)÷2 = 6km/ hour can be calculated according to the formula for calculating the water speed, and the sailing boat is being solved.

Baidu Encyclopedia-Problems of Running Water and Sailing Boat