There is a spring, pull it with 5N force, the total length is 12cm; if pull it with 10N force, the total length is 14N, find the original length of the spring

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• 1. The two balls a and B have the same mass m and are suspended at o point by two equal length thin wires. Between the two balls is a light spring with stiffness coefficient K When the spring is in the horizontal direction and the angle between the two thin wires is θ, the length of the spring is compressed mgtan (θ / 2) / K, why not 2mgtan (θ / 2) / k
• 2. A rope with length of L = 60cm is tied with a small ball, which moves in a circle in the vertical plane. Given the mass of the ball M = 0.5kg, find: (1) try to determine the minimum centripetal force when it reaches the highest point; (2) the minimum speed when the ball reaches the highest point and continues to move in a circle; (3) when the speed of the ball at the highest point is 3m / s, the pull of the rope on the ball. (g = 10m / S2)
• 3. 5. As shown in the figure: the mass of the wooden frame is m, the stiffness coefficient of the light spring is k, the spring is connected with the ball a, and the balls a and B are explained in detail with thin lines How is it stressed
• 4. As shown in the figure, balls a and B are connected by a light spring with a stiffness coefficient of K1, ball B is suspended at point o with a thin line of length L, ball a is fixed directly below point O, and the distance between O and a is L. at this time, the tension of the rope is F1. Now, the spring between a and B is replaced by a light spring with a stiffness coefficient of K2 to balance the system. At this time, the tension of the rope is F2, and the size relationship between F1 and F2 is () A. F1 ＞ f2b. F1 ＜ F2C. F1 = F2D
• 5. As shown in the figure, a and B balls are attached to the lower end of the vertical suspension light spring, and their mass ma = 0.1kg and MB = 0.5kg. When the spring is at rest, its elongation is 15cm. If the thin line between a and B is cut, what is the amplitude and maximum acceleration of a ball in simple harmonic motion?
• 6. The object with mass m decelerates and rises h under the action of constant force F in the vertical direction A. The gravitational potential energy increases mghb. The kinetic energy decreases FHC. The mechanical energy increases FHD. The increase of gravitational potential energy is less than the decrease of kinetic energy
• 7. As shown in the figure, the stacked objects a and B, under the action of constant force of size F, move in a straight line at a constant speed along the horizontal plane, then the correct conclusion in the following is () A. In Figure A and B, the friction force on object a is FB. In Figure A and B, the friction force on object B is FC. In figure a, the friction force on object a is 0, and that on object B is FD. In Figure B, the friction force on object a is f, and that on object B is f
• 8. The spaceship rises at a constant acceleration of a = G2. Due to the overweight phenomenon, the weight of an object with a mass of 10kg measured by a spring scale is 75n? (earth radius is 6400km, g = 10m / S2)
• 9. One person stands on the scale, its indication is 500N, another hanging spring scale bottom hangs an object of 300N When the person pushes up the object with a force of 100 N, what is the indication of the spring scale? What is the indication of the scale? When the person pulls down the object with a force of 50 N, what are the indication of the spring scale and the scale? Why?
• 10. When the object with a mass of 50g is suspended under the spring scale, when the spring scale moves upward with uniform acceleration and linear motion of 1.2m/s2, what is the indication? When the spring scale moves upward with uniform deceleration and linear motion of 1.2m/s2, what is the indication?
• 11. There is a spring with a length of 10 cm. After pulling it with a force of 5 N, the length becomes 12 cm. If pulling it with a force of 10 N, what is the length of the spring?
• 12. If a spring is pulled with 5N force, the total length is 12cm; if it is pulled with 10N force, the total length is 14cm, what is the original length of the spring?
• 13. The length of a spring is 12cm when there is no weight on the lower end, 15cm when there is a 0.6N object on the lower end and the spring is stationary. When there is a 1n weight on the lower end of the spring, the length of the spring is () A. 5 cmB. 17 cmC. 20 cmD. 7 cm
• 14. When a spring hangs an object of 0.5N for 12cm and an object of 1n for 14cm, the original length of the spring will be the same______ ．
• 15. How long is the original length of the spring? What is the stiffness coefficient of the spring?
• 16. The sliding blocks a and B with mass m and M 'respectively are stacked on a smooth horizontal table, as shown in the figure. The static friction factor between a and B is u'. The dynamic friction factor is u. The system was at rest. Now there is a horizontal force F acting on a, so that a and B do not slide relative to each other F
• 17. As shown in the figure, the small wooden block with mass m slides onto the original stationary wooden board with mass m at speed v0. The horizontal ground is smooth, and the length of the wooden board is L. when the wooden block moves to the other end of the wooden board, their speeds are V1 and V2 respectively, and the displacement of the wooden board is l0. The internal energy generated in this process is calculated
• 18. As shown in the figure, the slider with mass m is still on a smooth horizontal table. The bottom of the smooth arc surface of the slider is tangent to the table. A small ball with mass m rolls towards the slider at the speed v0. Suppose that the ball cannot pass the slider, we can find: (1) when the ball reaches the highest point, what are the speeds of the ball and the slider? (2) The maximum height at which the ball rises
• 19. The board with length L and mass m is still on a smooth horizontal table. A small block B with mass m falls on the left end of board a with horizontal velocity v0. The friction coefficient between board B and board a is u, and block B can be regarded as a particle. How large is V0 if B reaches the right end of board a at last
• 20. A long board with mass m is still on a smooth horizontal table. The small slider with mass m slides on the template from a section of the board at a horizontal speed v0 A long board with mass m is still on a smooth horizontal table. The small slider with mass m slides on the board at a horizontal speed V0 from a section of the long board until it leaves the board. The speed of the slider when it leaves the board is V0 / 3. If the template is fixed on the horizontal table, other conditions are the same, the speed v when Qiuhua leaves the board