The magnitude of sliding friction is related to the pressure on the contact surface and the roughness of the contact surface The size of sliding friction is related to the pressure on the contact surface and the roughness of the contact surface. Please design a simple experiment to verify that the size of sliding friction is related to the pressure on the contact surface. In addition to long wooden boards, there are iron blocks, aluminum blocks and wood blocks of the same quality. Each block is fixed with a small metal hook for traction, Fixed pulley, spring dynamometer, several thin wires

The magnitude of sliding friction is related to the pressure on the contact surface and the roughness of the contact surface The size of sliding friction is related to the pressure on the contact surface and the roughness of the contact surface. Please design a simple experiment to verify that the size of sliding friction is related to the pressure on the contact surface. In addition to long wooden boards, there are iron blocks, aluminum blocks and wood blocks of the same quality. Each block is fixed with a small metal hook for traction, Fixed pulley, spring dynamometer, several thin wires

1. Put the aluminum block on the regular wood plate, pull the aluminum block with a spring dynamometer to make a uniform linear motion, and record the indication F1 of the spring dynamometer
2. Stack the iron block on the aluminum block, pull the aluminum block with a spring dynamometer for uniform linear motion, and record the indication F2 of the spring dynamometer
3. Compare the size of F1F2 and draw a conclusion

The object is stationary on an inclined plane, and the contact surface is rough. Must the object be subject to friction? The object is also affected by wind

Yes. You can draw the stress analysis diagram. You can't stand still without friction

Is the magnitude of friction related to the contact surface of the object?

Independent of contact surface area
It is related to the roughness of the contact surface. The coarser the contact surface, the greater the friction
It is related to the pressure of the object on the contact surface. The greater the pressure, the greater the friction

There are six line segments with lengths of 1, 2, 3, 4, 5 and 6 respectively. Do any three of them form a triangle? What is the probability of forming a triangle?

This problem should be applied to the relevant knowledge such as permutation and combination, triangular trilateral relationship and probability. When the experts use the theoretical knowledge to solve it, I can only solve it intuitively. I don't know whether it is right or not: first, there are six line segments in a group of three [total C (6,3) = 20], which can be divided into 20 groups, respectively: 1.2.3; 1.2.4； 1...

Among the five line segments with lengths of 1, 2, 3, 4 and 5, the probability that the three line segments taken out are edges and can form an obtuse triangle is __

Take any three of the five line segments with lengths of 1, 2, 3, 4 and 5 respectively. There is C in all cases
three
five
=10 kinds,
Among them, when the extracted three sides can form an obtuse triangle, the cosine value of the largest side must be less than zero, that is, the sum of the squares of the smaller two sides is less than the square of the third side,
Therefore, there are only two methods to form obtuse triangle: 2, 3, 4 and 2, 4 and 5,
Therefore, the probability that the extracted three line segments are edges and can form an obtuse triangle is 2
10=1
5，
So the answer is 1
5．

Does the acceleration of a particle in circular motion point to the center of the circle

See if it is a uniform circular motion. If it is, it points to the center of the circle. If it is not accelerated along the tangential direction, the vector synthesis will not point to the center of the circle