The purpose of emphasizing "horizontal position" here is to balance the lever in horizontal position? . purpose,

Arm of force refers to the length of the vertical line from the fulcrum to the line of action of the force,
If the lever is not balanced in the horizontal position and the action line of the force exerted on the lever by the hook or object is vertical, then the arm of force is not on the lever, but in the air, so it is difficult to measure the length of the arm of force accurately
Therefore, the purpose of balancing the lever in the horizontal position is to make the arm of force along the lever, so as to measure the length of the arm of force

RELATED INFORMATIONS

1. What are the types and distribution of the world climate?
2. If PA = AAB (a belongs to R), then the trajectory equation of point Q (m, n) is? It's been a long time I hope I can write the steps clearly Especially the proof of straight line
3. In the triangle ABC, a equals 45 degrees, C equals 30 degrees, C equals 10, then a equals?
4. If the pointer of the instrument rotates 30 ° clockwise, it will be recorded as - 30 ° and then + 45 ° means -______ , 0 ° denotes______ ．
5. The equation of the circle with the focus of the parabola y * 2 = - 8x as the center and tangent to the Quasilinear of the parabola is?
6. It is known that the two focal points of hyperbola x2a2 − y2b2 = 1 (a > 0, b > 0) are F1 and F2. Point a is on the image of the first quadrant of the hyperbola. If the area of △ af1f2 is 1, and Tan ∠ af1f2 = 12, Tan ∠ af2f1 = - 2, then the hyperbolic equation is () A. 5x212− y23＝1B. 12x25−3y2＝1C. 3x2−12y25=1D. x23−512y2＝1
7. In the plane rectangular coordinate system, the end coordinates of line AB are a (- 2,4), B (4,2), and the line y = kx-2 has the intersection point a-5b-2c3d5 with line ab
8. If the circle x2 + y2 = 4 is known and the secant ABC of the circle is made through a (4,0), then the trajectory equation of the midpoint of the chord BC is () A. （x-2）2+y2=4B. （x-2）2+y2=4（0≤x＜1）C. （x-1）2+y2=4D. （x-1）2+y2=4（0≤x＜1）
9. Given that point P is a point outside circle C: x2 + y2 = 1, let K1 and K2 be the slopes of two tangent lines of circle C passing through point P respectively. (1) if point P coordinates are (2, 2), find the value of K1 · K2; (2) if K1 · K2 = - λ (λ≠ - 1, 0), find the equation of locus m of point P, and point out the type of conic where curve m lies
10. Is 2012 a leap year? How to calculate it
11. How to calculate the trapezoid area according to the median line?
12. The area of a rectangular desktop is one square meter, and the side length of a square desktop is nine tenths of a meter. How many square meters more is the area of a rectangular desktop than that of a square desktop% d% a
13. Ab ⊥ BD, CD ⊥ BD, B and D are perpendicular feet, ab = 2, CD = 3, P is the moving point of BD, let Pb = x, BD = y, make P and a, B, C, D form two similar triangles, Finding the function analytic expression of Y with respect to X Make point P form two similar triangles with a, B, C and D respectively
14. 1 / 4 of 1500 chickens and ducks raised in a farm is 15 less than 40 / 100 ducks (equation)
15. There are 1500 chickens and ducks in a feed factory. One quarter of the chickens are 15 less than 40% of the ducks. How many chickens and ducks are there in the feed factory?
16. There are 1500 chickens and ducks in a feed farm. One quarter of the chickens are 15 less than 40% of the ducks. How many chickens and ducks are there? The answer I know is the process, the process of calculation and the step-by-step calculation How to solve it It's not the same. My equation is: let's have X ducks Quarter (1500-x) = 40 ‰ X-15 375-X/4=0.4X-15 X=600 1500-600=900 So there are 600 ducks and 900 chickens. How does this formula come from?
17. The ratio of chickens to ducks is 5:2. After 120 chickens are sold, this is the ratio of chickens to ducks, which is 9:4
18. A total of 3870 chickens and ducks are raised in the farm. The number of chickens is 2.5 times that of ducks, and there are 20 more. Now all of them are sold. A chicken costs 4.5 yuan. How much is the total income of the farm
19. The feeding group raised a total of 1720 chickens and ducks, sold half of the chickens and bought 260 ducks. At this time, the number of chickens and ducks was equal
20. (1) A total of 1720 chickens and ducks were raised by the feeding group. Half of the chickens were sold and 260 ducks were bought. At this time, the number of chickens and ducks was the same How many ducks? (2) There are two reservoirs A and B. There are 3000 cubic meters of water in pool a and 1200 cubic meters of water in pool B. now the water is diverted from pool a to pool B at a flow rate of 50 cubic meters per minute. How many minutes later, the water storage in Pool B is twice that of pool a? (3) A total of 340 peach and apricot trees are planted in the orchard, of which the number of peach trees is three times more than that of apricot trees, 20 more. How many of the two kinds of trees are there? (4) There is 470 kg of oil in barrel a and 190 kg of oil in barrel B. how many kg of oil in barrel a can make barrel a oil twice as much as barrel B oil? There are a lot of questions. I really can't help it