How to exemplify the outstanding performance of the normative role of law

Imagine what it would be like if there were no law, which would highlight the important role of law

The title is as follows:
The displacement of an object moving in a straight line with uniform acceleration is 24m from the end of 2s to the end of 6S, and 40m from the end of 6S to the end of 10s?
My practice is different from that on the Internet. A friend wrote this:
We use the basic method:
Vt = VO + at S = VO + 0.5at ^ 2
If the initial velocity of the object is VO and the acceleration is a, then
1. The velocity of the object at the end of 2S is:
Vo2=Vo+a2s
The displacement in 4S from the end of 2s to the end of 6S is as follows
24m = VO2 t + 0.5 * a * T ^ 2, i.e
24m=(Vo+a2s)4s+0.5a(4s)^2 (1)
2. The velocity of the object at the end of 6S is:
Vo6=Vo+a6s
The displacement in 4S from 6S to 10s is as follows
40m = vo6 t + 0.5 * a * T ^ 2, i.e
40m=(Vo+a6s)4s+0.5a(4s)^2 (2)
(2) (1) the reduction is as follows
a=1m/s^2 (3)
(3) Substituting (1) to solve the problem
Vo=2m/s (4)
But if a = 1m is brought into the initial velocity every second, according to the formula s = V0 · T + 1 / 2 · a · T ^ 2
If we get 24 = v0.4 + 1 / 2.1.16, we can calculate V0 = 4, which is inconsistent with the previous answer V0 = 2. What's the matter?

Note that the first movement, from the end of 2s to the end of 6S, is not equal to V0 in the later movement
The last V0 is the first VT!

Wind speed 200 km / h, air density ρ = 1.3kg/m3, wave wall height h = 100m, total length L = 720m
When a hurricane hits the wall vertically, its velocity decreases to zero?

This is the theorem of momentum
We know the velocity of air flow V, the density ρ, and the area of the wall s = h * L
Then the mass of air hitting the wall in a period of time t is m = ρ * VT * s = ρ vthl
From the theorem of momentum: mv-0 = ft, we get ρ vthl * V = ft, we get f = ρ V & sup2; HL

In order to measure the acceleration of the slider on the air track, a light shield with a width of 0.5cm is installed on the slider. Under the action of traction, the slider first accelerates uniformly through two photoelectric gates, and the matching digital millisecond meter records the time of the light shield passing through the first photoelectric gate, which is 0.05s, The time to pass through the second photo gate is 0.01 seconds. The time from the first photo gate to the second photo gate is 2 seconds. Calculate the acceleration of the slider

It is known that the velocity through the first baffle V1 = 0.005 △ 0.05 = 0.1m/s, the velocity through the second baffle V2 = 0.005 △ 0.01 = 0.5m/s and V2 = V1 + a · T, so a = (0.5-0.1) △ 2 = 0.2m/s & # 178;

The length of the smooth slope is l, and the acceleration of two balls a and B on the smooth slope is 0.8g (the direction is downward along the slope). The ball a is released from the top of the slope by static, and the ball B moves upward along the slope with the speed V0 from the bottom of the slope. In order to make the two balls meet on the slope (excluding the lowest point and the highest point), what conditions does the initial velocity V0 of ball B satisfy?

When two small balls meet on the inclined plane (excluding the lowest point and the highest point), small ball B first makes a uniform deceleration motion upward along the inclined plane, and then makes a uniform acceleration motion downward along the inclined plane. When small ball B returns to the bottom of the inclined plane and small ball a also reaches the bottom at the same time, the speed V0 of small ball B is the minimum critical speed of meeting

A basic problem of physics speed in grade one of senior high school
The average speed of a person going up the mountain is 4m / s, and the average speed of going down the mountain is 6m / s. what is the average speed of the person in the whole journey
The answer is 4.8m/s, please tell me how to do it, it's better to have a detailed description, thank you

Let's assume that the distance is s
So the time to go up the mountain is s / 4, and the time to go down the mountain is s / 6
The average speed of the whole journey is equal to the total distance 2S divided by the total time (s / 4 + S / 6)
So v = 2S / (s / 4 + S / 6) = 48S / 10s = 4.8

Physics acceleration exercise foundation of senior one

(some pictures can't be uploaded. You can search by this version and find the corresponding pictures.)
Acceleration unit exercises
I. multiple choice questions
1. In studying the following motion, it is []
A. study the rotation effect of the earth B. study the rotation effect of table tennis
C. study the time required for trains to travel from Nanjing to Shanghai
D. study the time required for a train to cross the Yangtze River Bridge
2. The following statement is correct []
A. the speed of a moving object at a certain moment may be very high and the acceleration may be zero
B. the velocity of a moving object may be zero and the acceleration may not be zero at a certain time
C. It is impossible for the velocity to increase in the uniformly variable speed linear motion with positive initial velocity and negative acceleration
D. in the linear motion with constant velocity and positive acceleration, when the acceleration decreases, its velocity also decreases
3. For an object moving along a straight line, when the acceleration of the object gradually decreases, the following statement is correct
A. the speed of the object must increase; B. the speed of the object must decrease
C. The change of the speed of the object will decrease; D. the distance of the object will increase
4. Figure 1 shows the S-T image of a and B moving in a straight line relative to the origin of the same coordinate
A. both a and B move in a straight line with uniform speed change B. the distance between the starting points of a and B is S1
C. B starts earlier than a, T1 time D. B moves faster than a
5. For free falling motion, the following statement is correct []
A. in 1s, 2S, 3S The displacement ratio is 1:3:5:1
B. the ratio of velocity at the end of 1s, 2S and 3S is 1 ∶ 3 ∶ 5
C. The ratio of average velocity in the first second, second and third seconds is 1 ∶ 3 ∶ 5
D. the displacement difference between two adjacent 1s is 9.8m
6. When the object moves in a straight line with uniform acceleration, it is known that the velocity at the end of the first second is 6m / s, and the velocity at the end of the second second is 8m / s, then the following conclusion is correct []
A. the initial velocity of the object is 3m / s. B. the acceleration of the object is 2m / S2
C. the velocity change in any 1s is 2m / s. D. the average velocity in the 1s is 6m / s
7. In the V-T image shown in Fig. 2, it is []
　　
8. For an object moving in a straight line with uniform acceleration, suppose that the average speed of the whole course of its motion is V1, the speed at the middle moment is V2, and the speed at the half position of the whole course is V3, then the correct one in the following relation is []
　　A.v1＞v2＞v3　　B.v1＜v2=v3　　C.v1=v2＜v3　　D.v1＞v2=v3
9. The object Accelerates along a straight line. From the beginning of timing, the displacement is 1 m in the first second, 2 m in the second, 3 m in the third and 4 m in the fourth
A. the object must move in a straight line with uniform acceleration B. the initial velocity of the object is zero
C. the acceleration of the object is 1 m / S2 D. the average velocity of the object in the first four seconds is 2.5 m / s
10. When an object moves in a straight line with uniform acceleration, it successively passes through two points a and B. when passing through point a, the speed is VA, and when passing through point B, the speed is VB
　　
D. the instantaneous velocity passing through the midpoint of AB segment is equal to the ratio of the displacement of AB segment to the time taken
11. The maximum displacement of several objects moving in a straight line at a constant speed in the same time is []
A. object with maximum acceleration B. object with maximum initial velocity
C. the object with the highest final velocity D. the object with the highest average velocity
12. Figure 3 is the velocity graph of two objects moving in the same direction from the same place, where T2 = 2t1, then []
A. at T1, object B is in front and object a is in back. B. the acceleration of object a is greater than that of object B
C. two objects meet at T1 D. two objects meet at T2
Fill in the blanks
13. When a particle moves from the origin of the coordinate o along the y-axis to y = 4m, and then moves along the negative direction of the x-axis to the coordinate B (- 3,4), the distance of the particle moving from O to B is________ m. What is the displacement_________ m.
14. An object moves in a straight line with uniform acceleration from its rest. If the displacement within the second second is 6m, the acceleration is______ M / S2, the displacement in 5S is________ m. The first 18m of its motion is______ s. What is the displacement when the velocity increases from 6m / s to 10m / S__________ m.
15. When a car moves along a straight road, passing the first third of the journey at a constant speed of V1 = 25m / s, and passing the other two thirds of the journey at a constant speed of V2 = 50M / s, the average speed of the car in the whole journey is______ m/s.
16. The bullet can just pass through three boards of the same thickness stacked together (i.e. the bullet speed decreases to zero after passing through the third board). Assuming that the acceleration of the bullet moving in the board is constant, the time ratio of the bullet passing through the three boards in turn is_____________ .
17. The speed time image of an object moving in a straight line is shown in Figure 4
(1) the object is made in OA section________ The acceleration is__________ M / S2 in AB section________ Motion, acceleration is_________ m/s2.
(2) what is the velocity of the object at the end of 2S________ m/s.
(3) what is the maximum displacement of the object__________ m.
18. In the experiment of measuring the acceleration of linear motion with uniform speed change, fill in the blanks with the codes of the following steps in a reasonable order and write them on the horizontal line:_____________ .
(a) pull the paper tape, move the car to the place close to the clock, connect the power first, and then release the paper tape;
(b) fix the timer on the flat plate and connect the circuit well;
(c) a string is tied to the trolley, the string crosses the fixed pulley, and a hook code with proper weight is hung below;
(d) disconnect the power supply and remove the paper tape;
(E) raise one end of the plate and gently push the trolley so that the trolley can move at a uniform speed on the plate;
(f) fix the paper tape at the tail of the trolley and pass through the limit hole of the dot timer;
(g) replace with a new tape and repeat two or three times
19. The paper tape of a student's experiment is shown in Figure 5. Take o as the starting counting point. The counting points of t at the same time interval are a, B, C, D, e and f respectively. The distance between each adjacent two points is S1, S2, S3, S4, S5 and S6 in turn. If the acceleration is calculated at the time interval of 3T, the average acceleration is________ .
20. The record of the paper tape of an experiment is shown in Figure 6. The first few points in the figure are fuzzy, so take one counting point for every five points from point a, then the speed of the car passing through point D is zero________ M / s, the acceleration of the car is________ M / S2
3. Calculation
21. A particle starts to move in a straight line from its rest. In the first second, it moves at an acceleration of a = 1 m / S2. In the second second, it moves at an acceleration of a '= - 1 m / S2. In the third second, it moves at an acceleration of a = 1 m / S2. In the fourth second, it moves at an acceleration of a' = - 1 m / S2?
22. Car a starts to move in a straight line with uniform acceleration from standstill at an acceleration of 3m / S2, while car B starts to move in a straight line with uniform acceleration at an acceleration of 4m / S2 at the same place at a lag of 2S
(1) before car B overtakes car a, what is the maximum distance between two cars?
(2) how long does it take for car B to catch up with car a after departure? How far are they from the starting point?
　
　
　
Answers to unit exercises
I. multiple choice questions
　　1.C 2.AB 3.D 4.BD 5.CD 6.BC 7.B 8.C 9.D
　　10.AB 11.D 12.AD
Fill in the blanks
　　13. 7,5
　　14 4,50,3,8
　　15. 37.5
　　
17. Uniform acceleration line with zero initial velocity, 1. Uniform deceleration line with 4m / s initial velocity, - 2,2,12
　　18.E B F C A D G
　　
　　20. 2.48,6.18
　　

How to exemplify the outstanding performance of the normative role of law