1. There must be a physics knowledge point in senior one. Note 1
Explore elasticity 1. A deformed object will exert a force on the object in contact with it because it wants to return to its original state. This force is called elasticity.
2. The direction of elastic force is perpendicular to the contact surface of two objects, which is opposite to the direction of external force causing deformation and the same as the recovery direction. The elastic force of that rope is along the contraction direction of the rope; The elastic force of that hinge is along the direction of the rod; The elastic force of that hard rod may not be along the direction of the rod. The line of action of elastic force always passes through the contact point of two objects and is perpendicular to the tangent plane of the contact point.
3. Within the elastic limit, the elastic force f of the spring is proportional to the elongation or shortening of the spring, which is Hooke's law. F=kx .
4. K in the above formula is called the stiffness coefficient (coercive force coefficient) of the spring, which reflects the difficulty of spring deformation.
5. Series and parallel connection of springs: series connection:1/k =1/k1+kloc-0//k2 parallel connection: k=k 1+k2.
2. Senior one should take an examination of physics knowledge points.
The equilibrium of an object under * * point force 1 and the equilibrium state of an object under * * * point force.
(1) An object is said to be in equilibrium if it is stationary or moving in a straight line at a constant speed.
(2) When an object is at rest or moving in a straight line at a uniform speed, its speed (including size and direction) is constant and its acceleration is zero, which is the kinematic feature that the object is in a state of equilibrium under the action of * * * point force.
2. The equilibrium condition of an object under the action of * * * point force
The equilibrium condition of an object under point force is that the resultant force is zero, that is, F =0.
(1) Balance of two forces: two * * point forces must be equal in magnitude and opposite in direction and act on the same straight line.
(2) Three-force balance: the three * * * point forces must be in the same plane, and the resultant force of any two forces is equal in magnitude and opposite in direction, and acts on the same straight line, that is, the resultant force of any two forces must be balanced with the third force.
(3) If an object is in a state of equilibrium under the action of forces above three * * * points, orthogonal decomposition can usually be adopted, and there must be:
F = x = f 1x+f2x+...+fnx = 0。
F+y = f 1y+f2y+...+fny = 0。
2. Senior one requires one physics knowledge point induction note 2
1, elastic force (1) An elastically deformed object will exert a force on the object in contact with it. This force is called elasticity.
(2) To produce elastic force, two conditions must be met:
① Two objects are in direct contact;
② Two objects are elastically deformed when they are in contact.
2. Elastic force direction: the positive pressure between objects must be perpendicular to their contact surfaces. The pulling direction of the rope to the object always points to the direction in which the rope shrinks along the rope. When analyzing the pulling direction, the stressed object should be determined first.
3. Elasticity: Elasticity is related to elastic deformation. The greater the elastic deformation, the greater the elasticity. Spring force: F=Kx(x is elongation or compression, and k is stiffness coefficient)
4. How to judge whether there is elasticity between touching objects: If there is a small deformation between objects, it is not easy to detect, then the hypothesis method can be used to judge.
4. There must be a physics knowledge point in senior one. Note 4
Speed, average speed and instantaneous speed (1) represent the physical quantities of the object's speed, which is equal to the ratio of the displacement S to the time t taken for the displacement to occur. That is v = s/t, speed is a vector, which has both magnitude and direction, and its direction is the direction in which the object moves. In the international system of units, the unit of speed is (m/s) m/s.
(2) The average speed is a physical quantity describing the speed of a variable-speed moving object. If the displacement of a variable-speed moving object is s in a period of time t, we define v=s/t as the average speed of the object during this period (or during this period of displacement). The average velocity is also a vector, and its direction is the direction of the displacement of the object during this time.
(3) Instantaneous speed refers to the speed of a moving object at a certain moment (or a certain position). Physically, instantaneous speed refers to the average speed in a very short time near a certain moment. The magnitude of instantaneous speed is called instantaneous speed, or speed for short.
5. There must be a physical knowledge point in Senior One. Note 5
The acceleration of shifting is 1. The acceleration of an object is equal to the ratio of the velocity change (vt-v0) of the object to the time taken to complete this change.
a=(vt—v0)/t
2.a is not determined by △v and T, but by F and M. ..
3. Change = final value-initial value ... indicates the magnitude or quantity of change.
4. Change rate = change amount/time ... indicates the speed of change.
5. If the object moves in a straight line and the speed changes uniformly, the movement of the object is a straight line with uniform change (the acceleration does not change with time).
6. Speed is a state quantity, acceleration is a mass, and speed change (the degree of speed change) is a process quantity.
6. There must be a physical knowledge point in senior one. Note 6
Understand deformation 1. The shape and volume of an object change, which is called deformation for short.
2. Classification by form: compression deformation, tension deformation, bending deformation and torsion deformation.
According to the effect: elastic deformation, plastic deformation.
3. Judge whether there is flexibility:
1) Definition method (production conditions)
2) Moving method: assume that one of the elastic forces does not exist, and then analyze whether its state has changed.
3) Hypothesis method: suppose that one of the elastic forces exists, and then analyze whether its state has changed.
Elasticity and elastic limit
1. An object with the property of restitution is called elasticity.
2. The deformation that an object can completely recover after the external force is removed is called elastic deformation.
3. If the external force is too large, the shape of the object cannot be completely recovered after the external force is removed. This phenomenon is that the elastic limit of the object is exceeded and plastic deformation occurs.
7. There must be a physical knowledge point in senior one. Note 7
Law of Conservation of Mechanical Energy (1) Mechanical energy: the general term for kinetic energy, gravitational potential energy and elastic potential energy.
Total mechanical energy: E=Ek+Ep is scalar and relative.
The change of mechanical energy is equal to work without gravity (such as work done by resistance)
Δ δE = W Non-weight
Mechanical energy can be transformed into each other.
(2) Law of Conservation of Mechanical Energy: The kinetic energy and gravitational potential energy of an object only when gravity does work.
Mutual transformation occurs, but the mechanical energy remains unchanged.
Expression: Ek 1+Ep 1=Ek2+Ep2. Only gravity works.