How to solve the flow rate problem in the first year of junior high school?

This involves physics problems such as velocity synthesis.,Don't talk about it here.,Just tell you how to solve the problem.,If you want to know this kind of physics.,You can hi me.。 ）

Generally, the background of the topic is that it is going along or against the water, and what objects are moving in the water. (I don't know if your topic is a one-dimensional or two-dimensional background.)

If the object also has velocity, for example, the velocity is x m s, then the velocity of the water y m s, if it follows the water, the water will help the object, so that the object will move faster, then add the speed of the water, in fact, its motion speed is x+y m s., if it is against the water, it is x-y m sIn the water, the speed of the moving object changes due to the change of the moving body, and if you tell the distance again, you can find the time, and tell the time to find the distance.

I still have to say that the velocity of an object is relative, for example, I say that its velocity is x m s, which is relative to a stationary object, such as a motionless ground).

It's a bit verbose, I don't know if it's clear? If you don't understand, you can ask me.

Velocity against the water) 2 = velocity of the water.

Boat speed + water speed = downstream speed.

Boat speed - water speed = speed against the water.

Just these three formulas, everything is inseparable from them.

Solution: Let AB be at a distance of x km, and ship A will leave B at h km.

x (then {(x+y) (

From: x+x-10=20 From: x+y=20

2x= 30

x=15 brings x=15 into , getting: y=5

x=15 So: the solution of the system of secondary equations is {

y=5A: Ship A leaves place B for 5 km.

Distance Speed = Time.

lz, that's my answer.

AB is XKM away, and Ship A leaves B YKM

x/（（x+y）/（

Solve the equation yourself according to the distance velocity = time.

There are two scenarios for this question.

The land is between A and B, which is a c B

Solution: Let A to B take x hours and B to C take y hours.

x+y=4①

It's not between a and b, which is c, a b

x+y=4①

It's good to figure it out yourself)

AB is XKM away, and Ship A leaves B YKM

x/（（x+y）/（

Then solve it yourself.

1.A man was rowing in the river against the current, and when he passed through point A, the straw hat fell into the water, and he realized it 10 minutes later and immediately turned around and chased after him, 3600m downstream of point A. The velocity of the boat relative to the water is constant, and the velocity of the water flow is obtained.

2.The width of the river is 420m, the speed of the boat in the still water is 4ms, and the current speed is 3ms, so the shortest time for the boat to cross the river is found.

3.A boat has a speed of 15 km h in still water and a current speed of 3 km h. Going down the river at 12 noon, I asked how far the boat should go before returning to the starting point by 5 p.m.

4.The water conservancy survey team took a boat from place A down the river to place B, and immediately went upriver to point C again, which took a total of 4 hours. The speed of the ship in still water is one kilometer per hour, and the distance between A and C is 10 kilometers, so find the distance between A and B.

Summary: Actually, it is not difficult to solve these problems, as long as you figure out the relationship between this: Downstream velocity = hydrostatic velocity + water velocity; Reverse water velocity = hydrostatic velocity - water velocity This is easy to solve! Thank you!

Downwind travel time = distance (flight speed + wind speed).

Travel time against the wind = distance (flight speed - wind speed).

Solution: Let the speed of the aircraft be xkm h and the wind speed be ykm h.

Get: 10 3 (x-y) = 1200

From: x+y=480

Result: x-y=360

Solution: x=420, y=60

A: The speed of the aircraft is 420kmh and the wind speed is 60kmh

Let each flood gate discharge x meters per hour, and the water inlet per hour is as follows:

2y-2x=

8x-4y=

Find x,y last time equal to.