A problem that should be paid attention to when using spring balances Sun Deying is in the teaching of the third section of the third chapter of the "Phase" of the Pedagogical Edition of the People's Education Edition. The students do (Textbook 3-10).
After the mortar, it was found that the spring scale in (b) was reversed. According to the connection of the figure, it is actually equal to the gravity of the spring scale directly added to the system, which is equivalent to hanging the same quality as the spring balance at the right end of the rope. The hook code, in this way, the tension on the left end of the rope is equal to the sum of the tension of the spring balance (ie, the reading of the spring scale) and the gravity of the spring balance, that is, the balance of the spring balance is not equal to the tension of the rope when balancing ( Or the weight of the weight attached to the left end). We seem to have saved half of the force and can't get the conclusion that "the fixed pulley is not labor-saving". So, that. Under this condition, when the system is in balance, the tension on the right end of the rope is still equal to the sum of the force of the spring balance and the gravity of the spring balance. But at this time, the reading of the spring balance is equal to the tension of the rope, that is, the gravity of the code linked to the left end is equal. The work done by the friction of the entire path is 2, so the speed of the object sliding down the slope is greater than that of sliding along the curved surface. speed. So which kind of solution is correct, the difference between the two solutions is whether the elastic force is mgcos0 or whether the friction is equal to Vmgcos0 when the object moves along the surface. The analysis of the second solution is more reasonable, then the first type is wrong. Where, why is the extrapolation method we used in the past does not apply here? In fact, the block in Example 1 has no energy loss at point D of the intersection of two small slopes, and it is only a hypothesis to slide down the slope after collision. , the reason is not real, the reason is as follows: Assume that the object collides with the slope DC without energy loss (ie elastic collision), then the motion of the object along the slope is not sliding, but the elastic collision with the slope is carried out after the elastic collision; When the inclined surface slides, the positive pressure (N) of the object to the inclined surface is greater than the component force mgcos02 whose gravity is perpendicular to the inclined surface DC during the collision of the object D, so that the velocity of the object perpendicular to the inclined plane DC is reduced to zero, and at this time The frictional force (W) also acts more than the frictional force Mmgcos 02 when the object slides on the inclined plane DC. Therefore, the collision of the object at the point D is an inelastic collision, and the energy is lost. Therefore, the first method of solving problems cannot be extrapolated indefinitely. The problem is only an approximate, idealized estimate. In the case of Example 2, the support force of the object is greater than the component of gravity perpendicular to the surface, so Example 2 is not a generalization of Example 1, but a different problem.
From the above analysis, we can see that we must be cautious when using extrapolation.
These cool looking industrial water pipe design,add an vintage style to your living room,bedroom, office space,coffee shop or restaurant.
You can DIY any water pipe design you like such as table ,chair,shelf bed,wardrobe,door pull,hook,paper holder etc.
Tell us your idea about water pipe design,we can make any items you like.
Contact us for more information about the DIY Industrial Pipe Series.
Diy Industrial Pipe Series
Diy Industrial Pipe,Industrial Pipe Shelving,Diy Pipe Shelves,Industrial Pipe Shelving Diy
Foshan Nanhai Xin Jianwei Hardware Co., Ltd , https://www.aaghardware.com