Xiaoming starts from a at 8 a.m. and goes to B at 20 kilometers per hour. 15 minutes later, Xiaogang starts from a and goes to B at 6 kilometers per hour In B, Xiao Ming takes a 60 minute rest in B and then returns to A. on the way back, he meets Xiao Gang who starts from A. at this time, they are 2 kilometers away from B. find the distance between a and B

Xiaoming starts from a at 8 a.m. and goes to B at 20 kilometers per hour. 15 minutes later, Xiaogang starts from a and goes to B at 6 kilometers per hour In B, Xiao Ming takes a 60 minute rest in B and then returns to A. on the way back, he meets Xiao Gang who starts from A. at this time, they are 2 kilometers away from B. find the distance between a and B

15 points = 1 / 4
Suppose the distance between a and B is x km
（x+2-1/4×20）÷20+1=（x-2）÷6
3x-9+60=10x-20
7x=71
x=71/7
A: the distance between a and B is 71 / 7 km

Xiaohua, Xiaogang and Xiaobing each took out the same money to buy exercise books. When taking them, Xiaohua took 10 more than Xiaogang, and Xiaogang took 4 more than Xiaobing. Xiaohua should give Xiaobing 1.44 yuan. How much is each exercise book
Better not use the equation

Xiaohua has 10 more than Xiaogang and Xiaogang has 4 more than Xiaobing,
So Xiaohua and Xiaogang are more than Xiaobing (10 + 4) + 4 = 18 (Ben)
Among them, Xiaohua has 10 + 4 = 14 more than Xiaobing, and keeps 18 △ 3 = 6,
Take 14-6 = 8 more and pay 6-4 = 2 to Xiao Gang,
Give Xiaobing 8-2 = 6, so each book is 1.44 △ 6 = 0.24 (yuan)

How many a is 100 Ma, how many a is 50 Ma, how many Ma, how many Ma is the quintic power of 2x10

100 μ a = 10 ^ (- 4) a,
50 Ma = 0.05 a = 5 * 10 ^ 4 μ a,
The fifth power of 2x10 μ a = 200 Ma

On the experiment of Newton's second law
Under the premise that the mass of the weight is far less than that of the trolley, the pulling force on the trolley is approximately equal to the gravity of the weight
Why?
Make it clear//

This is a connectome problem
According to Newton's law
For the whole system, there is m weight * g = (M weight + m car) * a
A = m weight * g / (M weight + m car)
For weights, there are m weights * G-F, rope tension = m weights * a
F rope tension = m * G -- m * a
It can be seen that only when the acceleration a is not large can the pull force on the trolley be approximately equal to the gravity of the weight, and because a = m weight * g / (M weight + m car), that is to say, the mass of the weight is far less than the mass of the trolley

The triangle has an area of 275cm and a height of 11cm

Let the bottom of triangle be xcm
From the triangle area formula, 11x / 2 = 275, the solution is x = 50
A: the triangle bottom is 50cm

A bottomless wooden box with mass m is placed on the horizontal ground, a light spring is suspended on the top of the wooden box, and the other end is suspended

1. When hanging AB, the spring elongation is x, 2mg = KX, x = 2mg / K
2, only hang a, spring elongation x0, Mg = kX0, x0 = mg / K
3. After cutting the thin line between AB, a makes a simple harmonic motion, its equilibrium position is at x0, and its amplitude is x-x0 = mg / K
Therefore, the upward pressure of the spring on the top of the box is mg, and the pressure of the wooden box on the ground is mg mg

In the four mixed operations, we can use () to reduce the number of calculation, or use () to simplify the calculation

In the four mixed operations, we can use (reduction) to reduce the number of calculation, or use (general) to simplify the calculation
Please click the "select as satisfactory answer" button below,

The mass of a and B is m a and M B respectively, and m a = 2m B. their dynamic friction coefficient is the same as that of the horizontal table. When they slide on the table with the same initial kinetic energy, the ratio of their maximum sliding distance is ()
A. 1：2B. 2：1C. 1：1D. 1：2

According to the kinetic energy theorem, there are: for a: - μ m a, GS1 = 0-ek ① For B: - μ M B, GS2 = 0-ek ② So S1S2 = m b m a = 12 & nbsp; so D

The sum of the first n terms of the arithmetic sequence an is Sn, and A2 equals negative 5, A4 minus A6 plus 6 equals 0;
(3) When SN is greater than 0, the minimum value of n is obtained

If A2 = - 5, a6-aa4 = 2D = 6, then d = 3, so an = 3n-11. ① A1 = - 8; ② S10 = 10A1 + 10 * 9 * D / 2 = 55; ③ an = 3n-11, Sn = n [A1 + an] / 2 = n (3n-19) / 2, then when Sn > 0, n > 19 / 3, that is, the smallest n is 7

When the car runs at a constant speed on a straight road, the acceleration when braking is 4m / S2. After 5 seconds, the car stops and the speed when driving at a constant speed is calculated

Reverse thinking
v=at=4*5=20m/s