A brick factory can make 80 million bricks a year. A brick is 24cm long, 12cm wide and 6cm thick. With these bricks, a wall with 24cm wide and 2m high can be built. How long is the wall? fast

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• 1. 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
• 2. 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
• 3. 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
• 4. 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
• 5. 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
• 6. How long is the original length of the spring? What is the stiffness coefficient of the spring?
• 7. 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______ ．
• 8. 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
• 9. 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?
• 10. 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?
• 11. When a spring oscillator vibrates harmonically, when its displacement from the equilibrium position is 1 / 4 of the amplitude, what is its kinetic energy? 15/16
• 12. A brick factory can make 80 million bricks a year. One brick is 24cm long, 12cm wide and 6cm thick. How long is the wall built with these bricks, 24cm wide and 2m high? Find the solution of the formula
• 13. Uncle Li uses 24cm long, 12cm wide and 6cm thick bricks to build a 1.8m long, 24cm wide and 9dm high rectangular brick wall in the yard. How many bricks are used for this wall
• 14. When t = 0, x = 12cm, the direction is positive. How long does it take to return to the equilibrium position?
• 15. How many pieces do you need to make the smallest square with a kind of rectangular board 20cm long and 12cm wide?
• 16. How many planks does it take to make the smallest square with a rectangle 12cm long and 8cm wide?
• 17. A rectangular board, can you cut this board into two pieces, and then put it together into a square desktop? Please draw a picture to show your spelling. The side length of the square How much is it? It's 18 decimeters long and 8 decimeters wide
• 18. How much work is done to pull a spring from 10 cm to 13 cm, the stiffness coefficient is 200 N / m
• 19. How much tension is used to lengthen a spring with a stiffness coefficient of 200N / m from 50cm to 70cm?
• 20. A light spring with stiffness coefficient of 200N / m, the original length is 20cm, when its deformation is 10cm, the spring state and elastic force are () A. The spring must be in tension. B. the spring may be in compression. C. the spring force is 40nd. 20n