Solve the first and second physics problems I don t know how to write the format .

Analysis: This lady clearly misunderstands speed.

What the lady is talking about is only one factor, and speed is related to time and distance.

The police said that 60 km h is the speed calculated by dividing the distance by time, and it is made in km h.

Answer: The speed of an object's motion is expressed in terms of velocity, which is equal to the distance traveled per unit of time.

60km h means 60km in 1 hour, and the unit time is 1 hour; The unit time used by the lady is 7 minutes.

Because the lady traveled 7 km in 7 minutes (60 7h), v=s t=60kmh

We also did this question when we were in the second year of junior high school.

The answer is in four steps.

The lady was wrong. 1 point).

She didn't figure out the concept of speed. 1 point).

The traffic police emphasize the ratio of the distance traveled in a unit of time to the time. 2 points) and the emphasis is on the time spent on a fixed distance. 2 points) Hope it helps.

Overspeeding refers to the "instantaneous speed" at a certain time, while the woman refers to the "average speed" at the time.

You can convert km h to m s, km h is the official designated unit, 40km h=, that is, this explanation can be done.

(1) Find the speed of car A first, the speed of car A is 54km h, which is 54000m h 3600s h=15m s

If two cars drive in opposite directions, then the distance of car A moving from phase to separation + distance of car B = 100m + 150m = 250m, and the moving time of the two cars is the same, that is, 250m = 10m s*t + 15m s*t to get t = 250m 25m s=10s

So the elapsed time from phase encounter to separation is 10 s

2) From car A to car B to car B, car A overtakes car B, and the distance of car A is 100m+150m=250m

The relative velocity of the two is 15-10=5m s

Then the time is 250m 5m s=50s

Known : V A = 54 km H = 15 m Sv B = 10 m S

L A = 100m

l B = 150m

Find t1 t2

Solution: t1=s v=(lA+lB) (vA+vB)=(100+150) (10+15)=10s

t2=s v=(lA+lB) (vA-vB)=(100+150) (15-10)=50sA: ....

1. Known: V1 = 200km H S1 = 1100km = S2 V2 = 80km H T1 = 9H

Seek: t2-t1

Solution: Composed of v=s t

t2=s2 v2=......

So t2-t1=......

A: ......It's okay to do the math yourself, right?!

2. Known: s=217km t=11:00 - 9:30=1:30=

Seeking: v flat. Solution: v flat = s t = ......

A: ......3. Known: s=30km t=

Seek: v truth. Solution: v real = s t = ......=150km/h

Here we must make a comparison between v real and v = 120km h, greater than or equal to speed, less than or equal to not speed. ）

Because it was 150km h 120km h, the car was speeding.

…So kind......We have ...... questions in the final exams of the second year of the year

Known: V sound = 340m s s gold = 884m t = find out: how fast the sound propagates in the metal tube.

Solution t empty = 884m 340m s =

T gold = so v gold = 884m Answer......

Solution: It is known that the propagation speed of sound in the air is 340m s, and the length of the metal tube is 884m, and the time taken for sound to propagate in the relative tube is faster than in the air.

The time it takes to propagate flowers in the air: 884m 340m s = so the time it takes to propagate flowers in metal.

So the speed of propagation in the metal is 884m A......

Physics problems are actually solved by mathematical means after the solution is deduced from physical ideas.

Solution: Let the distance of the truck and the sedan move is s, and the sedan will catch up with the truck after the time t. Then there are:

For trucks: s=40*(2+t).

For cars: s=80*t

From the above two formulas, it can be deduced:

t=。。。A: ......

First of all, calculate the gravity of the pure divine power of water: gravity = mass * g

Mass = Volume * Density.

Volume = Base Area * Height.

So volume = 2*

Mass = here g press 10

Calculate) gravity = 2n

Pressure = gravity = 2n

Pressure to do potato loss = pressure area = 1000 pascals.

Pressure hand guess = gravity = 2*g

20n2) pressure = gravity of water + gravity of container = 20 + 2 = 22n3) pressure = pressure area = 22 pascal.

6、c9、b

10. 6V (when S1 is closed, R2 has been short-circuited to destroy Hongxin, only R1 works, and the electric gear gauge measures the voltage of the power supply, which is 6V; The current is 6V 20 ohms =

The rest is right.

Known: M cup = 30g M liquid = 110g - 30g = 80g V liquid = 100cm3

Seeking: P liquid. Solution: Tan Xiao rent p liquid = m liquid let Zhao Shen take v liquid = 80g 100cm3 = =