In medical biological experiments, Drosophila melanogaster is often used as the test object. In a cage with 6 Drosophila melanogaster, two flies are accidentally mixed into the cage (at this time, there are 8 flies in the cage: 6 Drosophila melanogaster and 2 flies), so we have to open a small hole in the cage, let the flies fly out one by one, until both flies fly out, and then close the hole. (I) just one Drosophila melanogaster is left in the cage (II) the probability of at least five flies remaining in the cage

In medical biological experiments, Drosophila melanogaster is often used as the test object. In a cage with 6 Drosophila melanogaster, two flies are accidentally mixed into the cage (at this time, there are 8 flies in the cage: 6 Drosophila melanogaster and 2 flies), so we have to open a small hole in the cage, let the flies fly out one by one, until both flies fly out, and then close the hole. (I) just one Drosophila melanogaster is left in the cage (II) the probability of at least five flies remaining in the cage

Let AK (k = 0,1,2,3,4,5,6) be the event with exactly k flies left in the cage. (I) there is exactly one fly left in the cage, that is, the seventh fly flies out, while there are one fly and five flies out of the first six flies; there are A87 basic events, which are equally possible, among which there are c21c65a66 target events, P (A1) = c12c56a66a78 = 314; (II) there are at least 5 flies left in the cage The results show that the event A5 + A6, P (A5) = c12c16a22a38 = 114, P (A6) = a22a28 = 128, and the event A5 and A6 are mutually exclusive, P (A5 + A6) = P (A5) + P (A6) = 114 + 128 = 328; that is, the probability of exactly one fly remaining in the cage is 314, and the probability of at least five flies remaining in the cage is 328

There are three red balls and two white balls in the pocket. The texture is uniform and the shape is exactly the same. If you feel two balls from them, the probability that both are red balls is high______ ．

There are 20 cases in total, and there are 6 cases in which both are red balls, so the probability is 310

After transforming the radical 8, 12, 18 and 32 into the simplest quadratic radical, randomly select one of them, and the probability that it can be the same as the root number of 2 is 0______ ．

First of all, the above four formulas are transformed into the simplest quadratic radicals, which are 22, 23, 32 and 42 respectively. If one of them is randomly selected, the chance of each radical being extracted is equal, and there are four kinds of results. If there are three results that can be extracted with the same number of square root of 2, then p (the number of square root that can be extracted with the same number of square root of 2) = 34

Acceleration formula derivation, please write the process and usage
For example, what formula should be used only for distance and time? What formula should be used for problems with different quantities and the same quantity

Kinematics 1. Average velocity VT / 2 = s / T (definition) 2. Useful inference VT ^ 2 – VO ^ 2 = 2As 3. Velocity VT / 2 in the middle time = (VT + VO) / 2 4. Final velocity VT = VO + at 5. Velocity vs / 2 in the middle position = [(VO ^ 2 + VT ^ 2) / 2] 1 / 2 6. Displacement S = VT ^ 2 T = VT + at ^ 2 / 2 = VT / 2T 7. Acceleration a = (VT vo

It's a mental arithmetic problem, not a practical one. The more the better,
You don't have to add and subtract

1+16=
2+13=
5+7=
2+9=
4+9=
1+5=
6+8=
13+5=
18-3=
19-6=
5-3=
4-3=
18-8=
15-1=
17-6=
20-11=

Angular acceleration formula and its application
2n π = 1 / 2 α T ^ 2 this formula is seen in other places. The title is that it takes 3.3 seconds for a part to accelerate from rest to the maximum speed, and it turns 14 turns in total. This formula solves this problem, but I haven't seen it in other places. It should come from a variant,

This is the formula of constant angular acceleration from static acceleration angle, n is the number of turns, a is angular acceleration, pushing down is to integrate the definition of angular acceleration with time twice

100 oral arithmetic questions in grade one

425
55+5+8

Angular acceleration α = w / T
Then w = angle / T
Can we deduce the formula: α = angle / T ^ 2

Similarly, it is the derivative of angular velocity, α = Δ ω / Δ t

Mental arithmetic within 100

75+27= 68-19= 38+59= 78-49= 67+25= 57-38= 46+46= 64-57= 29+47= 67-59= 16+67= 54-48= 54+46= 71-65= 54+36= 48-39= 49+49= 91-85= 36+14= 25+41= 79-64= 19+21=11－9＝ 15－6＝ 32－2＝ 50＋1＝ 30＋2＝ 16－9＝...

Acceleration is determined by force, and there is a formula; angular acceleration is determined by what, and there is a formula

The angular acceleration β = DW / DT, if it is a uniform acceleration motion, there is a formula such as β = w / T 2 β Φ = W2 - W1, the moment M = J · β, j is the moment of inertia, this formula is similar to Newton's second law in translational mechanics