Take any two balls from the pocket with two red balls and two white balls. In the following groups, the two events are mutually exclusive and not antagonistic______ (please write down all the serial numbers you think meet the requirements) ① at least one white ball; all white balls; ② at least one white ball; at most one white ball; ③ exactly one white ball; exactly two white balls; ④ at least one white ball; all red balls

Take any two balls from the pocket with two red balls and two white balls. In the following groups, the two events are mutually exclusive and not antagonistic______ (please write down all the serial numbers you think meet the requirements) ① at least one white ball; all white balls; ② at least one white ball; at most one white ball; ③ exactly one white ball; exactly two white balls; ④ at least one white ball; all red balls

Taking two balls from the red bag containing two red balls and two white balls, there are three situations: "two white balls", "one white ball and one red ball" and "two red balls"

How to calculate the probability of mutually exclusive independent events
Given two probabilities, which event is multiplication and which event is addition

Independent event refers to: in a randomized trial, two events such as a and B are independent of each other, whether one event occurs has nothing to do with whether another event occurs, which is suitable for the multiplication principle P (AB) = P (a) P (b)
Mutually exclusive event means that two events such as a and B can not happen at the same time in a random trial, that is, P (AB) = 0

Mutual exclusion and the probability of independent events
Given that a and B are mutually independent events, B and C are mutually exclusive events, P (a) = 0.55, P (b) = 0.35, P (c) = 0.15, P (A and C) = 0.12, find the probability of at least one of the three events

P (aubuc) = P (a) + P (b) + P (c) - P (A and b) - P (A and C) - P (C and b) + P (A and B and C) where p (A and B and C) = 0 = P (b and C) because B and C cannot occur together, P (A and b) = P (a) * P (b) = 0.1925 because a and B are independent events. Finally, the data p (aubuc) = 0

How to do the second problem

After X hours
35x＋45x＝10×2
100x＝20
x＝4/1
That is: 4 / 1 hour = 15 minutes
A: after 15 minutes
It should be

Calculation of acceleration
When the car is advancing at the speed of 10m / s, it suddenly finds a bicycle at 6m ahead is advancing at the same speed of 4m / s, and the car brakes immediately. In order to ensure that the car does not touch the bicycle, try to find the minimum acceleration of the car brake

When the car just touches the bicycle, the speed is exactly 0, which is the minimum acceleration
Set the braking time as t
In this period of time, the bicycle walking distance is 4T
Then the braking distance of the car is 4T + 6
Using the distance formula s = VOT - (1 / 2) at × t
Since the final velocity is 0, 0 = VO at
a=Vo/t
All the formulas are substituted into an equation and converted into an equation only containing T. the solution is t = 6S
A = 5 / 3
Typing is not easy. Give me points

When a team of players was trained, all the players moved forward at 35 km / h. Suddenly, the 1 player marched on the speed of 45 km / h, and after 10 km, she turned the car back and still rides back at 45 km / h until she joined the other players. How long time did the 1 players start from the team to meet the players again?

How to calculate instantaneous velocity and acceleration

The instantaneous velocity is defined by the average velocity. The average velocity is the change of displacement divided by the change of time. When the change of time is very small, the change of displacement is also very small, and the position will be very close to the starting position. When the time is infinitely small, two positions can be considered to coincide, so the average velocity can be considered as the instantaneous velocity, The instantaneous velocity at the starting point can be calculated by the operation of mathematical limit. The starting point can be any point on the way. Acceleration is the change of instantaneous velocity divided by the change of time
I'm a sophomore in senior high school. When calculating the acceleration, I usually use the square of the final velocity minus the square of the initial velocity, which is equal to twice the acceleration times the displacement. This formula is only limited to uniform acceleration or Newton's second law, △ s = at ^ 2, or use the definition. According to the problems I have done, this is generally the case in mechanics. It should be enough

In ancient times, there was a wise minister in a certain Kingdom who invented chess and presented it to the king. Since then, the King became addicted to playing chess. In order to thank the wise minister, the king agreed to meet a request of the minister. The minister said, put some grains of rice on the chessboard, one grain of rice in the first grid, two grains of rice in the second grid, four grains of rice in the third grid, and then eight grains of rice, 16 grains of rice All the way to the 64th grid. "You're stupid. You want so much rice." the king laughed
(1) How many meters should be put in the 64th grid? (expressed by power)
(2) Please explore the number at the end of the number in (1) (write the inquiry process briefly)
(3) How much rice should the king give the minister?

Subtract one from 64 of 1 2
Two is eight
The total number of 3-meter grain is 2 ^ 0 + 2 ^ 1 + 2 ^ 2 +. + 2 ^ 63 = 2 ^ 64-1 = 18446744073709551618
According to the calculation of 50 grams of 600 grains of ordinary rice, the total weight is about 1531.1 billion tons

Is a free falling body an infinite acceleration?
I suddenly thought of a physical problem. I know that a free falling body is accelerated. I would like to ask, is the free falling body accelerating infinitely, even exceeding the speed of light or several times the speed of light, or can it maintain a speed drop after reaching a certain speed?
I seem to understand. What I understand from your answers is that a free falling body will accelerate infinitely, even faster than the speed of light, if it is only subject to gravity and no other external forces, but it will not be in that ideal state. In fact, the falling body will be affected by a variety of external forces in addition to gravity, and the falling body will eventually reach a kind of balance under the influence of a variety of external forces and fall at a fixed speed. Of course, a variety of external forces are changing at any time, and the falling body will continue to reach the balance again. As we say, the object will be solved by others, which should also be decomposed in order to achieve a kind of balance . Please give me more advice!

In fact, our answers are different, but they all have some truth, especially the point of view that the speed reaches a certain value. It takes into account the change of resistance
In fact, raindrops falling from high altitude have a constant speed when they approach the ground
In other words, "the acceleration of gravity equals g" has a certain scope of application. It is generally believed that it is on the "surface" of the earth, that is, it is not far away from the center of the earth. (according to the law of universal gravitation, G = GM earth / R & sup2; = 9.8, R,),
Therefore, the displacement of a free falling body is limited to a certain extent, and its maximum value is r-r. therefore, the object cannot be accelerated endlessly. As for the influence of air resistance, we should also analyze the specific situation. At this time, even the object cannot be equivalent to a particle. We should consider not only the mass of the object, but also the shape and volume of the object
In fact, the building owner confuses two problems: (1) the relationship between the motion of a free falling body and the change of resistance (controlled by the displacement, i.e. the displacement cannot exceed the maximum displacement); (2) under the action of constant external force, can an object accelerate infinitely (beyond the speed of light)? According to the theory of relativity, the speed of light is the limit of the motion speed of all objects, As the speed of an object approaches the speed of light, its mass will increase

The fourth chapter exercises of mathematics in the first issue of grade seven of Beijing Normal University Edition
Such as the title
Don't download it

The seventh grade mathematics midterm test paper (students, it's time to show yourself, you have to think carefully, calm answer paper ah!) 1, carefully choose a choice (3 points for each question, a total of 30 points) 1, the square root of 1, is () a, 4b, ± 4C, 2D, ± 22, the correct is () a, B, C, D, 3, in the following