How is science in primary school
Publish: 2021-04-27 17:10:06
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there will be bitcoin chain and Ethereum chain when choosing the recharge address of the exchange. If you have a good choice, you can contact bitcom online customer service
2. You can't withdraw money, can you? help
3. To solve the problem of friction, you must understand the concept of friction, that is, the conditions under which friction occurs
the so-called friction is the force that hinders the relative motion of an object, and the direction of friction is opposite to the motion direction or relative motion direction of the object
the conditions of friction are: (1) two objects must contact each other 2) There is a squeeze between two objects 3) There is a tendency of motion or relative motion between two objects
1. When an object is stationary on a horizontal plane, if it is not pushed or pulled, it will not be affected by friction. If thrust or pull is received, it belongs to the category of static friction. The size of friction is equal to that of pull or thrust, and has nothing to do with the gravity or pressure of the object. Only the maximum static friction is related to the pressure or gravity on the object
2. If the object is pressed against the wall, the friction force is equal to the gravity of the object
3. As long as the object moves in a straight line at a constant speed on the horizontal plane, the object is subject to the action of balance force in the horizontal direction, that is, the thrust or pull force is equal to the friction force
4. If the object is not pushed by a force of 10N, the object is subjected to static friction, which is equal to the thrust. Just push with 15N force, and the friction force on the object is the maximum static friction force. If the thrust force is increased later, the friction force will not change. Theoretically, the sliding friction of objects is less than the maximum static friction, but it is generally considered that they are equal
5. Pull a 10N object with 15N force to move vertically and uniformly, then the friction force is f = 15-10 = 5N
if you understand my answer above, I think you will have a better understanding of friction force!
the so-called friction is the force that hinders the relative motion of an object, and the direction of friction is opposite to the motion direction or relative motion direction of the object
the conditions of friction are: (1) two objects must contact each other 2) There is a squeeze between two objects 3) There is a tendency of motion or relative motion between two objects
1. When an object is stationary on a horizontal plane, if it is not pushed or pulled, it will not be affected by friction. If thrust or pull is received, it belongs to the category of static friction. The size of friction is equal to that of pull or thrust, and has nothing to do with the gravity or pressure of the object. Only the maximum static friction is related to the pressure or gravity on the object
2. If the object is pressed against the wall, the friction force is equal to the gravity of the object
3. As long as the object moves in a straight line at a constant speed on the horizontal plane, the object is subject to the action of balance force in the horizontal direction, that is, the thrust or pull force is equal to the friction force
4. If the object is not pushed by a force of 10N, the object is subjected to static friction, which is equal to the thrust. Just push with 15N force, and the friction force on the object is the maximum static friction force. If the thrust force is increased later, the friction force will not change. Theoretically, the sliding friction of objects is less than the maximum static friction, but it is generally considered that they are equal
5. Pull a 10N object with 15N force to move vertically and uniformly, then the friction force is f = 15-10 = 5N
if you understand my answer above, I think you will have a better understanding of friction force!
4. 1. Research questions: what is the relationship between the size of friction force
2. Make a hypothesis: the size of friction force is related to the roughness of the contact surface and the positive pressure
3. Experimental materials: Spring dynamometer, small block with pull ring, weight, wood and glass plate with different roughness
4 Research plan:
basic experimental method: control variable method
experimental steps: A. firstly, put the small block on the long board, pull the animal block horizontally and slowly with the spring dynamometer, and quickly read out the indication X1 of the spring Dynamometer when the block is first pulled; Put a weight on the small block, pull the indicator x2 as described above, and then put a weight to read the indicator X3, and compare the readings for three times
B. place the small block on the glass plate, pull the small block as above, read out the indication X4 of the spring dynamometer, add one weight at a time, read out the indication X5 and X6 with two weights, and compare X1 and x4, X2 and X5, X3 and X6
5. Observation data and experimental records
just make up a few numbers by yourself. If you really want to research, do it at home. Anyway, the operation of the experiment is very simple
X1 = 3, X2 = 4, X3 = 5,
X4 = 1, X5 = 2, X6 = 3,
(it's better to draw a table and separate it with the horizontal and vertical lines of the head)
6. Analysis of experimental results:
by comparing x1, X2, X3 and x4, X5, X6 horizontally, we can see that with the increasing pressure of the block on the board, the minimum force of pulling the block is greater, that is, the greater the friction
longitudinal comparison of X1 and x4, X2 and X5, X3 and X6 shows that e to the different roughness of wood and glass, the minimum force required to pull the animal block is different, that is, the maximum friction of the object block on the wood is different from that of the object block on the glass, The friction between the object and the glass plate is less than that between the object and the board< 7. Research conclusion: friction is related to positive pressure and roughness of contact surface
PS: this research report is typed by myself, not copied
in addition, it's amazing to express one's own opinion that primary school began to write this kind of thing, and the experimental report can't be judged by the number of words. It's not hard to imagine the present situation of China with this kind of insidious and hypocritical ecation method
finally, good luck to you
2. Make a hypothesis: the size of friction force is related to the roughness of the contact surface and the positive pressure
3. Experimental materials: Spring dynamometer, small block with pull ring, weight, wood and glass plate with different roughness
4 Research plan:
basic experimental method: control variable method
experimental steps: A. firstly, put the small block on the long board, pull the animal block horizontally and slowly with the spring dynamometer, and quickly read out the indication X1 of the spring Dynamometer when the block is first pulled; Put a weight on the small block, pull the indicator x2 as described above, and then put a weight to read the indicator X3, and compare the readings for three times
B. place the small block on the glass plate, pull the small block as above, read out the indication X4 of the spring dynamometer, add one weight at a time, read out the indication X5 and X6 with two weights, and compare X1 and x4, X2 and X5, X3 and X6
5. Observation data and experimental records
just make up a few numbers by yourself. If you really want to research, do it at home. Anyway, the operation of the experiment is very simple
X1 = 3, X2 = 4, X3 = 5,
X4 = 1, X5 = 2, X6 = 3,
(it's better to draw a table and separate it with the horizontal and vertical lines of the head)
6. Analysis of experimental results:
by comparing x1, X2, X3 and x4, X5, X6 horizontally, we can see that with the increasing pressure of the block on the board, the minimum force of pulling the block is greater, that is, the greater the friction
longitudinal comparison of X1 and x4, X2 and X5, X3 and X6 shows that e to the different roughness of wood and glass, the minimum force required to pull the animal block is different, that is, the maximum friction of the object block on the wood is different from that of the object block on the glass, The friction between the object and the glass plate is less than that between the object and the board< 7. Research conclusion: friction is related to positive pressure and roughness of contact surface
PS: this research report is typed by myself, not copied
in addition, it's amazing to express one's own opinion that primary school began to write this kind of thing, and the experimental report can't be judged by the number of words. It's not hard to imagine the present situation of China with this kind of insidious and hypocritical ecation method
finally, good luck to you
5. The following conditions should be satisfied to proce friction.
1. The contact surface must be rough< Second, there must be extrusion
thirdly, objects must have movement tendency.
1. The contact surface must be rough< Second, there must be extrusion
thirdly, objects must have movement tendency.
6. The car's tires have deep tread patterns, in order to increase friction.
7. When calculating the size of friction, we should first judge whether the friction is sliding friction or static friction. And then it is solved by the corresponding method
the calculation formula of sliding friction is f= μ N. In the formula μ Dynamic friction coefficient, also called sliding friction coefficient, is only related to material and roughness of contact surface, but has nothing to do with contact area; N is the positive pressure
sliding friction: the force that occurs between two objects that contact each other and slide relatively, and prevents them from sliding relatively
the direction of friction is opposite to the direction of relative motion or the trend of relative motion. Instead of moving in the opposite direction of the object. Friction can be used as power or resistance
static friction: there is no formula for calculating the maximum static friction (approximately equal to sliding friction)
sliding friction: dynamic friction coefficient f= μ N f is the pressure of the object (not gravity), μ Is the dynamic friction coefficient, n is the positive pressure
rolling friction: (essentially static friction) should not be
the calculation formula of sliding friction is f= μ N. In the formula μ Dynamic friction coefficient, also called sliding friction coefficient, is only related to material and roughness of contact surface, but has nothing to do with contact area; N is the positive pressure
sliding friction: the force that occurs between two objects that contact each other and slide relatively, and prevents them from sliding relatively
the direction of friction is opposite to the direction of relative motion or the trend of relative motion. Instead of moving in the opposite direction of the object. Friction can be used as power or resistance
static friction: there is no formula for calculating the maximum static friction (approximately equal to sliding friction)
sliding friction: dynamic friction coefficient f= μ N f is the pressure of the object (not gravity), μ Is the dynamic friction coefficient, n is the positive pressure
rolling friction: (essentially static friction) should not be
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