"Balance of Common Point Force" Force and Balance PPT

Description

"Balance of Common Point Force" Force and Balance PPT

Part One: Learning Objectives

1. Understand the concepts of equilibrium state and balancing force.

2. Know the equilibrium conditions of common point forces and be able to use the equilibrium conditions to solve practical problems in life and production.

3. Will analyze dynamic balance issues.

Balance of common point force PPT, part 2: exploration of new knowledge

basic training

1. The equilibrium state of an object

An object remains in the state of ________ or ____________ under the action of a force.

2. Balance conditions for common point forces

Under the action of common point force, the equilibrium condition of an object is _________.

self-test

Thinking Analysis

(1) An object with zero speed must be in equilibrium. ()

(2) An object with a constant velocity must be in equilibrium. ()

(3) An object with constant speed must be in equilibrium. ()

basic understanding

(1) The famous scenic spot-Huangshan Flying Stone stands alone on the cliff. What forces act on it? What is the relationship between the magnitude and direction of these forces? What are the characteristics of their combined force?

(2) The high-speed train moves forward at a constant speed on a horizontal track. What forces act on it? What is the relationship between the magnitude and direction of these forces? What are the characteristics of their combined force?

(3) What is the physical state of the motion of the two objects in the picture?

Tips: (1) Due to gravity and support force, the gravity is vertically downward, the support force is vertically upward, the two forces are equal and opposite, and the resultant force is zero.

(2) It is subject to four forces: gravity, support force, traction force, and resistance. The gravity and support forces are equal and opposite, while the traction and resistance are equal and opposite, and the resultant force is zero.

(3) Equilibrium state.

The balance of common forces PPT, the third part: teacher-student interaction

understanding of the equilibrium state of objects

【Core Deepening】

1. Understand the equilibrium state from the perspective of kinematics: an object in equilibrium is at rest or in a state of uniform linear motion. In this state, its acceleration is zero, that is, the acceleration of an object in equilibrium is zero; conversely, an object with zero acceleration must be in equilibrium. state.

2. Understand the equilibrium state from a dynamic perspective: the net external force on an object in equilibrium is zero, and conversely the net external force on an object is zero, so it must be in equilibrium.

3. Static balance and dynamic balance

(1) Static equilibrium is equilibrium in a stationary state, and the resultant force is zero.

(2) Dynamic equilibrium is the equilibrium state of uniform linear motion, and the resultant force is zero.

4. Equilibrium state and balance of forces

Regarding the equilibrium state, which of the following statements is correct ()

A. When the speed of an object is equal to zero, the object is in equilibrium

B． A moving object must not be in equilibrium

C. If the object's state of motion remains unchanged, the object is in equilibrium

D． When an object is in equilibrium, it must not be acted upon by external forces

Error-prone reminder

The difference between "still" and "v=0"

(1) The object remains at rest: It means v=0, a=0, the resultant external force on the object is zero, and the object is in equilibrium.

(2) There are two possibilities for the object’s movement speed v=0:

①v=0, a≠0, the resultant external force on the object is not equal to zero, the object does not remain stationary and is in a non-equilibrium state, such as the object thrown to the highest point.

②v=0, a=0, this situation is consistent with the static state in (1).

Static equilibrium problem of common point forces

【Core Deepening】

1. The balance condition of common point force: If the resultant force of common point force is zero, then the resultant force in two mutually perpendicular directions must also be zero, that is, Fx sum = 0, Fy sum = 0.

2. Four common corollaries of equilibrium conditions

(1) Two force balance conditions: the two common point forces are equal in magnitude and opposite in direction.

(2) Three force balance conditions: When three common-point forces are balanced, the resultant force of any two of them must be equal to the third force, opposite in direction, and on the same straight line.

(3) When an object is in equilibrium under the simultaneous action of n common point forces, the resultant force of these forces in any direction is zero. The resultant force of any (n-1) force must be equivalent and opposite to the nth force, acting on the same straight line.

(4) When an object is in equilibrium under the action of multiple common-point forces, the forces connected end to end must form a closed polygon.

3. Steps to solve problems using equilibrium conditions

(1) Clarify the research object (object, particle or knot of rope, etc.).

(2) Analyze the motion state of the research object and determine whether the object is in equilibrium.

(3) Carry out force analysis on the research object and draw a force diagram.

(4) Establish an appropriate coordinate system, apply the equilibrium conditions of common point forces, and choose an appropriate method to formulate the equilibrium equation.

(5) Solve the equation and discuss the results.

Key competency 1: Understanding of equilibrium conditions

(Multiple choice) It is known that n forces at the same point are balanced, then the correct one of the following statements is ()

A. Among them, the resultant force of (n-1) forces is equal to and opposite to the n-th force.

B． The resultant force of three of the forces is in the same large and opposite direction as the resultant force of the remaining (n-3) forces.

C. The resultant force of n forces is zero

D． If (n-2) of the forces are removed, the object must be unbalanced

Key ability 2: Application of single object equilibrium conditions

Use a net bag to hang a football at point A on a smooth wall. The contact point between the football and the wall is B. The mass of the football is m. The angle between the suspension rope and the wall is α. The mass of the net bag is not included. Find the pulling force of the suspension rope on the ball. And the wall's support for the ball.

[Ideas] To solve this problem, follow the following ideas:

(1) Make a correct force analysis diagram using the ball as the research object.

(2) According to the force characteristics, the synthesis method, decomposition method and orthogonal decomposition method can be used to analyze and solve the problem.

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For more information about the PPT courseware "Force and Equilibrium Common Point Forces and Balance", please click the Force and Equilibrium ppt Balance of Common Point Forces ppt tag.

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Update Time: 2024-09-19

This template belongs to Physics courseware Lu Ke Edition High School Physics Compulsory Course One industry PPT template

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