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The probability of light burden, high efficiency and simple things in Mathematics (1)
I'm in sixth grade
A mathematical probability problem
It's a question of American college entrance examination. The translation is not very good
A coin is tossed four times. If the number of times of tossing a coin to the front is n, the probability of tossing a coin to the front is p
The following table shows the relationship between X and
x p
0 1/16
1 1/4
2 n
3 1/4
4 1/16
What's the probability of throwing four times and getting two positive times, that is, the value of N
Who can tell me about the analysis process? Thank you
dial the wrong number
The number of times to throw the front is X
I don't understand the answer to the problem of level 1 in sat 2
The answer is 3 / 8
The probability of all cases is 1
1/16+1/4+n+1/4+1/6=1,
The solution is n = 3 / 8,
But there seems to be something wrong with the question?
Because it is an equal probability event, the probability of a coin toss is 1 / 2
The probability of positive zero is 1 / 2 * 1 / 2 * 1 / 2 * 1 / 2 = 1 / 16
But the probability of one or three positive times should not be 1 / 4, but 1 / 2 * 1 / 2 * 1 / 2 = 1 / 8
2 of the answer probability tree who need to know the tell yo, rob
Born under the sky——
No longer have it, we are chaff, see
The equation that contained all his efforts: wires, instruments,
I wish the season would wear me out
I put out a hand
The seal, and some different shapes of mood ha ha
What is the difference between the classical view of time and space and the view of time and space of special relativity
Maybe classical mechanics thinks that time and space are absolute,
People in different states of the same event measure the same situation
The theory of relativity holds that different people in the same event measure different times,
According to the theory of relativity, the speed of light is the same for anyone, so the classical mechanics is different when the time is different
Relativity is a basic theory about space-time and gravity, which was founded by Einstein. It is divided into special relativity (special relativity) and general relativity (general relativity). The basic assumptions of relativity are the principle of invariable speed of light, the principle of relativity and the principle of equivalence. Relativity and quantum mechanics are the two basic pillars of modern physics, Relativity solves the problem of high-speed motion; quantum mechanics solves the problem of micro subatomic motion. Relativity has greatly changed the "common sense" concept of the universe and nature, and put forward new concepts such as "simultaneous relativity", "four-dimensional space-time" and "curved space"
Special relativity
Special relativity is the theory of relativity which only discusses the inertial frame. Newton's space-time view thinks that space is flat, isotropic and isotropic three-dimensional space, and time is independent of space in one dimension (so it is absolute). Special relativity thinks that space and time are not independent of each other, but a unified four-dimensional space-time whole, There is no absolute space and time. In special relativity, the whole space-time is still flat, isotropic and isotropic, which is an ideal condition corresponding to the "global inertial frame". Special relativity takes the speed of light in vacuum as a constant as the basic assumption. Combined with the principle of special relativity and the properties of space-time, Lorentz transformation can be deduced
General relativity
General relativity is a theory published by Albert Einstein in 1915. Einstein put forward the "equivalent principle", that is, gravity and inertial force are equivalent. This principle is based on the equivalence between gravitational mass and inertial mass (it is confirmed by experiments that there is no difference between gravitational mass and inertial mass within the accuracy range of 10-12), Einstein extended the principle of relativity in the narrow sense to the principle of general relativity, that is, the form of physical laws is invariable in all reference systems. The motion equation of an object is the geodesic equation in the reference system. The geodesic equation has nothing to do with the properties of the object itself, It only depends on the local geometric properties of space-time. Gravity is the expression of the local geometric properties of space-time. The existence of material mass will cause the curvature of space-time. In the curved space-time, the object still moves along the shortest distance (that is, along the geodesic motion - that is, straight-line motion in Euclidean space), such as the geodesic motion of the earth in the curved space-time caused by the sun, In fact, it goes around the sun, causing gravitational effect. Just as on the curved earth surface, if it moves in a straight line, it actually goes around the big circle on the earth's surface
Xiaohua can do 12 mental arithmetic problems per minute, which is two-thirds of Xiaojun's speed. How many mental arithmetic problems can Xiaojun do per minute?
Problem solving method
① Looking for unit "1"
② Unit "1" unknown, Division
③ Corresponding quantity / corresponding score = "1"
12 / 2 / 3 = 18
The following statement is consistent with the space-time view of special relativity
A. Two events occurring simultaneously in one frame of reference are not simultaneous in another frame of reference
B. The clock moves faster relative to the observer
C. When the object is still relative to the observer, its length measurement is the smallest
D. The mass of the object decreases with the increase of the velocity
A
After finishing 25 oral arithmetic questions, Xiaobin spent 3 minutes and made 2 mistakes. The correct rate was (). Xiaobin's average number of questions in 1 minute accounted for () / ()
The correct rate was 92%
(25) / (3) of the total
What is the difference between special relativity and general relativity
Special relativity: space and time change with the motion of matter, mass changes with motion, and mass and energy transform each other
General relativity: the existence of matter in space-time determines how space-time bends, and the curvature of space-time determines how matter moves. Since matter moves, space-time influences each other
In a narrow sense, we only think that time and space, matter is affected by motion
Mixed exercises within 30
8+7-3+5-9-8+6＝6
The problem of light cone, on the space-time view of special relativity
Is the set of all the points contained in the upper half of the light cone all the possibilities of this event? I want to say, for example, an event P in the light cone can be related to the cone top o with the speed lower than the speed of light, but not necessarily the two events have causality. We can only say that the two events can be related with the speed lower than the speed of light, that is to say, the point and the vertex in the light cone are not necessarily related
I don't know what you mean by the upper half of the light cone. The set of points in the light cone is the set of all the events that can be affected
No, as long as any two events can be connected, they will certainly have an impact. I just don't know what the impact is
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