Hooke's Law

(1) The spring is elastically deformed by external force, thus producing elastic force. Within the elastic limit, the elastic force f of the spring is directly proportional to the length x of the spring extension (or shortening). that is

F= kx

(2) Stiffness coefficient K refers to the spring force per unit length of the spring, and the unit is n/m. Its size is determined by the material of the spring, the length of the spring and the thickness of the spring steel wire.

X refers to the deformation variable, which should be the difference between the length of the spring after deformation (including tensile deformation and compression deformation) and the original length of the spring.

(3) Hooke's law is applicable within the elastic limit of the spring.

Example analysis (no diagram here, sorry):

Example 1. An object falling freely along a vertical wall is only in contact with the wall, and there is no extrusion. Neither the object nor the wall is deformed, so the wall has no supporting effect on the object. (as shown on the left in the figure below)

Example 2: For an object resting on an inclined plane, the supporting force of the inclined plane to the object is perpendicular to the inclined plane. (Bottom right)

Example 3: Chopsticks are placed in a hemispherical bowl, and the elasticity of chopsticks is analyzed (as shown).

Description:

Where point o is the center of the circle.

Example 4: Analyze the elasticity of a smooth ball.

Example 5. Draw the elastic force of each object A below and point out the object applying force.

Force application object: inclined plane force application object: ball and ground force application object: horizontal ground

Example 6: The original length of a spring is 10cm, and a 40N weight is hung at the lower end. In equilibrium, its length is 12cm. So when the spring is pulled, its length is 13cm?

Answer:

Let Zhang Liwei F2.

∵∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴∴875

∴f 1 = kx 1 = k(l 1-l0)= g

F2=kx2=k(l2 - l0)

Two types of division

F2=60N

Exercise questions:

1.(1) _ _ _ _ _ _ is called elastic force, and the condition of elastic force is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

(2) The content of Hooke's Law to study the spring force is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

2. There is a spring, the original length is 10cm, and the weight of 20N is 1 1cm. When the length of the spring is 13cm, what is the tension on the spring?

3. The stiffness coefficient of a spring is k = 5×103 n/m. When it is extended by 2.5cm, what is the elastic force? 100N How much will it stretch?

4. The original length of a spring is 10cm, the acting force is 10N, and the length is 12cm. Find the stiffness coefficient of this spring.

5. There is a spring with a stiffness coefficient of 50 N/m. How much force is needed to stretch it by 4cm? When the tension is 8N, how much does the spring extend? How much tension does it take to stretch the spring by 30 cm?

Reference answer:

1.

(1) The deformed object will be deformed by the force acting on the object in contact with it because it wants to be restored to its original state, and the deformation size is opposite to the deformation direction.

(2) The elasticity of the spring is directly proportional to the elastic deformation of the spring, and F=kx.

2.60N，

3. 125n； 2 cm

4.5 N/cm

5.2N 16cm； 15N。