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Youjiajia mathematics classroom
Release date: February 2020-18 19: 59
defy hardship and danger
basic knowledge
1. Elasticity: The property that an object will deform when stressed and return to its original state when it is not stressed.
2. Plasticity: the property that some objects can't automatically recover after deformation.
The discrimination between elasticity and plasticity depends on whether an object can automatically recover after deformation.
3. Elasticity: The force generated by the deformation of an object is called elasticity.
4. We often say that pressure, supporting force and pulling force belong to elasticity. The conditions for producing elastic force are: first, two objects are in contact with each other, and second, there is extrusion or stretching between objects.
5. Spring dynamometer
(1) Usage: Measure force.
(2) Principle: Within the elastic limit, the greater the tension on the spring, the longer the extension of the spring.
(3) Usage: Observe the range and dividing value of the spring dynamometer before use, and the measured force should not exceed its range; Check whether the pointer of the spring dynamometer is on the zero scale line, if not, adjust the pointer to the zero scale line; When measuring, the stress direction of the spring dynamometer should be along the axis direction of the spring; When reading, the line of sight must be perpendicular to the dial.
Online practice
1. Among the following four forces, the one that is inelastic is ().
A. the pressure of athletes on the springboard
B. Tension of stretching spring opponent
C. the attraction of the earth to the moon
D. the support of curved bamboo to birds
2. Of the following statements about the conditions for producing elastic force, the correct one is ().
A. Elastic force can be generated even when objects are not in contact with each other.
B. As long as two objects touch, they will produce elastic force.
C. only the spring can produce elastic force.
D. When two objects are in direct contact, they are elastically deformed when they are pressed against each other, thus producing elastic force.
3. As shown in the figure, the measuring range and dividing value of the spring dynamometer are ().
A.0~5 N、0. 1 N B.0~5 N、0.2 N
C.0~ 10 N、0. 1 N D.0~ 10 N、0.2 N
4. Several students use the same spring stretcher to exercise, and each student can pull the spring stretcher until the arm is straight, so the maximum pulling force on the spring stretcher when the arm is straight is ().
A. several students are the same age. The student with the longest arm. C. the heaviest student. D. The most powerful students
5. Without considering the gravity of the spring scale, Party A and Party B pull the same spring scale in the opposite direction with a force of 10 N, and the reading of the spring scale is ().
10 N C.0 N D.5 N
6. As shown in the figure, the spring dynamometer has a unified scale [] (fill in "Yes" or "No"), the range is [] n, the dividing value is []N, and the reading is [] n. ..
7. The experimental device for physics team to explore the relationship between spring elongation and tension is shown in Figure A. 。
When the elongation of (1) spring is 3.5cm, the Zhang Liwei on the spring is _ _ _ _ _ n.
(2) According to the data in the table, within the elastic limit, the elongation of the spring is _ _ _ _ _ _ _ _ _ _ _.
Reference answer
CDBBB is 0~5 0.2 2.6 1.75.
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