How many more than 4-digit, 8-digit, to list one by one, you can use the 10 numbers 1234567890, 4-digit is OK, 8-digit input is OK I forgot my cell phone password. I want all of them

How many more than 4-digit, 8-digit, to list one by one, you can use the 10 numbers 1234567890, 4-digit is OK, 8-digit input is OK I forgot my cell phone password. I want all of them

If you try one every second, you need 1157 days, about 39 months
I suggest you think of another way

The four numbers 3456 can be used to form () three digit numbers without repetition. The sum of these three digit numbers is ()?

The sum of these three digits is (119988)

In the ten numbers of 0-9, the sum of two three digit numbers is equal to a four digit number. It requires that the two three digit numbers are different from the four digit numbers
Talk about ideas or specific program algorithms

The best algorithm is to add all the three digits. If there is no same number in the two three digits and the sum is four digits, and all the ten digits are not equal, it will be printed out. This algorithm should be better, and it is not difficult to realize

At x0, the velocity is V0 and the acceleration is - KX (k positive constant). The motion equations of velocity V and X are obtained

This is the case of DV / DV / dvdv / DV / DV / DX / dvdv / DX / dvdvdv / DX / DX, and it is the case of dvdv / dvdvdvdvdvdv / DV / DV / DX / DX / DX / DX / DX / DX / DX / DX / DX / dvdv / DX / DV / DX / DX / DX / DX, and as a = - KX \\\\\\\\\\\\\\\\\\\\\\\\\\\\\35;178;; V & #178; + KX & #178; = VO & #178

There is a horizontal conveyor belt with a speed of, on which there are two points a and B with a distance of 10m. Now, a workpiece is placed at point a, which starts to move from rest and arrives at point B in 6S. Ask the acceleration of the workpiece moving between a and B and the speed of the conveyor belt when it reaches point B in the shortest time
The speed is 2m / s

(1)1/2at^2+v(6-t)=10;
at=2;
The solution is t = 2;
a=1;
(2)1/2at^2=10;
And a = 1;
v=at;
V = 2 * radical 5

Mechanical physics of frictional motion
The angle of inclination is 37 degrees, the speed is 10 meters, the friction coefficient is 0.5 per second, the length of AB is 16 meters, and the time required to rotate a to B clockwise and counterclockwise is calculated

Kinematic mechanics help within 24 hours processing
The wood blocks slide on the horizontal static conveyor belt of L = 18m at the horizontal speed of V0 = 6m / s, and can move from the a end to the B end after t = 6S
Calculate (1) dynamic friction coefficient between wood block and conveyor belt
(2) If the conveyor belt rotates clockwise with v 1 = 4 m / s and the block is put on the conveyor belt without horizontal initial speed, it indicates the movement of the block
(3) How long does it take to get to B
If you can also teach me how to look at the difficulty (depending on the situation, plus points AB is both ends)

From the displacement time formula, 18 = 6 * 6-0.5 μ g * 6 ^ 2 is μ = 0.1 (2). In the process of uniform acceleration, a = 1m / S ^ 2T = (v-v0) / a = 4sx = (V + V0) t / 2 = 8m ＜ 18m wood blocks should be uniformly accelerated first, and then with the belt. (3) T1 = 4st2 = x / v = 10m / 4m / S = 2.5st =

Physics topics in mechanics and kinematics
1. A particle moves along a circle with radius r = 0.5, and the kinematics equation is θ = 3 + 2T ^ 2, then the tangential acceleration of the particle t is? The normal acceleration is?
2. An object with mass m is ejected obliquely from the ground at an initial velocity VO and a projectile angle θ = 45 degrees. If the air resistance is not taken into account, when the object falls to the ground, its momentum increment is?
Please give an analysis,

1) D θ / dt = w = 4T, and WR = V, so the normal acceleration a = V ^ 2 / r = 8t ^ 2
Tangential acceleration B = RDW / dt = 2
2) There is no increment in the horizontal direction, only I = (2 ^ 1 / 2) MV in the vertical direction

Ask a question about physical mechanics
.
When the bus runs at a constant speed on a straight road, is the person standing in the bus stressed in the horizontal direction? Why? If it is in the vertical direction?
Is that person affected by the traction of the car? Why?

In the horizontal direction without force, the car is moving at a constant speed, and the person is also moving at a constant speed, which means that the person is balanced in the horizontal direction. There are two possibilities: one is not under force, and the other is under a pair of balanced forces. But if under a balanced force, there must be two forces acting in the horizontal direction. In fact, there are no two forces acting in the horizontal direction, so there is no force

As shown in the figure, one end of the light rope with length L is fixed at o point, and the other end is tied with a small ball with mass M. at the lowest point, give the ball a horizontal initial velocity v0. At the same time, apply a force F with constant size and direction perpendicular to the rope. When the ball moves to the rope level along the circle, the velocity of the ball is exactly v0. Calculate the size of F
The answer is to use the kinetic energy theorem in one step. I mainly want to ask how to calculate the work done by the pulling force which is changing in this direction. The answer is that the work done by the pulling force is: FL multiplied by two-thirds... Why?

Work is scalar and has no direction
As long as the pulling force is in the same direction as the object's motion, the work done by the pulling force is w = FS
In this problem, the direction of the pulling force is always the same as that of the object, so
W = FS, s is one fourth of the circumference length, i.e. L * Pai / 2
So w = fl * Pai / 2