How to prove the second Kepler theorem?

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• 1. According to the law of conservation of mechanical energy The content of the law of conservation of mechanical energy says that only gravity (or spring force) does work. Does that mean that only spring force does work, and other forces can't?
• 2. The results are as follows: 1. The ball moves from point a to point B with the initial velocity V, and then returns automatically. The velocity of the ball passing through point a is () (the picture of this question is: A is on a horizontal track, moving for a period of time and then on an inclined plane, the height of the inclined plane is h, and the highest point is b) 4 options A radical (V ^ 2-4gh) B radical (4gh-v ^ 2) C radical (V ^ 2-2gh) D radical (2gh-v ^ 2)
• 3. The condition of the law of conservation of mechanical energy It is said in the book that the condition of conservation of mechanical energy is that the work is only done by gravity or elastic force. An object sliding on a smooth slope is only subject to gravity and supporting force, so its mechanical energy is conserved. However, if a crane lifts an object, its mechanical energy is not conserved, but it is only subject to gravity and tensile force. We all know that tensile force is also elastic force, so why? According to the book, the condition for the conservation of mechanical energy is that it is only affected by gravity or elastic force
• 4. As for the applicable conditions of the law of conservation of mechanical energy, the correct one in the following statement is () A. When there are other external forces, as long as the combined external force is zero, the mechanical energy is conserved. C. when there are other external forces, as long as the work of the resultant force of other forces is zero, the mechanical energy is conserved. D. when the projectile flies in the air without resistance, it is only affected by the heavy force, so the mechanical energy before and after the explosion is conserved
• 5. What are the conditions of the law of conservation of momentum, the law of conservation of kinetic energy and the law of conservation of mechanical energy, What's the difference?
• 6. How to design experiments in physics to prove that air resistance affects the falling of objects?
• 7. Considering the air resistance, is the falling time of different objects at the same height related to the density? As the title!
• 8. On the conservation law of physical mechanical energy The radius of the smooth track fixed in the vertical plane is r, and a small ball with mass m moves in a circle on the track in an anti clockwise direction. If the pressure of the ball on the track is 8 mg at the lowest point a, the pressure on the track is 8 mg when the ball moves to the highest point B______ The answer is 2mg, but I don't know why
• 9. Law of conservation of mechanical energy The trolley with mass m and length L stops on a smooth horizontal plane, and the small block with mass m is placed on the leftmost end of the trolley. Now, a right water balance force F is applied on the small block to make the block move uniformly and linearly from the static state. The friction force between the block and the trolley is f '. When the block slides to the rightmost end of the trolley, the distance of the trolley is s. in this process, when the block slides to the rightmost end of the trolley, the distance between the block and the trolley is s, Is the added mechanical energy of block and trolley FS? Why?
• 10. In the experiment of using free falling motion to verify the law of conservation of mechanical energy: if the instantaneous velocity is calculated and verified by measuring the distance between two points on the paper tape, the distance between point 2 and point 4 is S1, the distance between point 0 and point 3 is S2, and the period of tapping is t The relation of T = 0___ ．
• 11. A problem of quadratic term theorem Known xy
• 12. A problem of remainder theorem When f (x) = 2x ^ 3 + ax ^ 2 + BX + 3 divided by (x-1) (x + 2), the remainder is (2x + 1) a) f(1),f(-2) b) Two equations with a and B as unknowns are established c) Find the values of a and B
• 13. Remainder theorem If we divide the polynomials f (x) and G (x) by 2x ^ 2-3x-2, we can get the co expressions 2x + 3 and 4x-1 respectively, then the co expressions obtained by dividing f (x) - G (x) by 2x + 1 are
• 14. The problem of quadratic term theorem The example in the book is to find the coefficient of X3 in the expansion of (x-1 / x) 9 I use the permutation and combination method C6 9 * (- 1) 6, and the result is 84 or - 84. Which step is wrong?
• 15. Under what circumstances does weda's law fail? RT OK = = in fact, I've got the answer I want, but it seems to be true many times? The plural is also true
• 16. What is substance? What is its theoretical significance? An introduction to the basic principles of Marxism
• 17. Veda's theorem (relation between root and coefficient) If X1 and X2 are two parts of the equation AX ^ 2 + BX + C = 0 1. Two positive roots 2. Two negative roots 3. One positive root and one negative root Both are bigger than one 5. One is bigger than one, and the other is smaller than one 6. One is bigger than 1, and the other is smaller than 0 7. Both of them are between 3 and 4
• 18. Theoretical yield coefficient
• 19. In △ ABC, it is known that ab = 102, a = 45 ° and the length of BC side is 202033 and 5 respectively, then the corresponding angle c is obtained
• 20. In the acute angle △ ABC, the opposite sides of angles a, B and C are a, B and C respectively. If AB + Ba = 6cosc, then the value of tanctana + tanctanb is______ ．