"Exploring the Function of Pulleys" Force and Machinery PPT Courseware 3

Description

"Exploring the Function of Pulleys" Force and Machinery PPT Courseware 3

1. Learning objectives

1. What is a fixed pulley? What is the use of fixed pulleys? What are the characteristics?

2.What is a moving pulley? What is the function of using a movable pulley? What are its characteristics?

3. What is a pulley block? What is the purpose of using a pulley block? What are the characteristics?

Ask students to use their brains to think and solve the above problems based on the experiments in the previous class.

2. Understand the movable pulley and fixed pulley

When the pulley is in use, it is divided into fixed pulley and movable pulley according to whether the position of the shaft moves.

When in use, the shaft is fixed and is called a fixed pulley.

When in use, the shaft and the weight move together, called the pulley.

Solving doubts and exploring (1): Characteristics of fixed pulleys

A: The fulcrum is at the axis O.

B: Power arm l1 is equal to resistance arm l2

1. The fixed pulley is actually an equal-arm lever.

2. The pulling force is always equal to the gravity of the heavy object. F=G

Solving doubts and exploring (2): Characteristics of moving pulleys

A: The fulcrum is at edge O

B: The power arm l1 is twice the resistance arm l2.

The power F is 1/2 times the resistance G F=1/2G

1. The moving pulley is essentially a lever whose power arm is twice the resistance arm.

2. The direction of the pulling force is the same as the direction of movement of the weight. vertically upward)

3. Understand the pulley block

Although fixed pulleys can change the direction of force and make our work convenient, they cannot save labor.

Although the moving pulley can save half the force, it cannot change the direction of the force, which often makes it inconvenient to use.

So people used fixed pulleys and movable pulleys in combination, combining their respective advantages to form a pulley block.

4. Classroom exercises

1. As shown in Figure (a), object B weighs 100N. When it rises at a constant speed under the action of force F, F should be equal to ____N. (excluding friction)

2. As shown in Figure (b), the weight of object A is 100N, and the tensile force endured by the hook hanging the heavy object is ______N. The force exerted by a person pulling the rope at a constant speed is ＿＿＿N (the dead weight of the movable pulley is not included)

Class summary:

1) Using a fixed pulley does not save effort, but the advantage is that it can change the direction of force. The fixed pulley is essentially an equal-arm lever.

2) The moving pulley can save half the force and cannot change the direction of the force. The moving pulley is essentially a lever whose power arm is twice the resistance arm.

3) Using a pulley block can not only save effort, but also change the direction of force.

When using a pulley block, which uses several lengths of rope to lift an object, the force used is a fraction of the weight of the object.

Keywords: Forces and Machinery Teaching Courseware, Exploring the Function of Pulleys Teaching Courseware, Guangdong and Shanghai Version 8th Grade Physics Volume 2 PPT Courseware Download, 8th Grade Physics Slide Courseware Download, Forces and Machinery PPT Courseware Download, Exploring the Function of Pulleys PPT Courseware Download ,.PPT format;

For more information about the PPT courseware "Force and Machinery Exploring the Function of Pulleys", please click the Force and Machinery PPT Exploring the Function of Pulleys PPT tag.

"Exploring the Function of Pulleys" Force and Machinery PPT Courseware 2:

"Exploring the Function of Pulleys" Force and Machinery PPT Courseware 2 Fixed Pulley and Movable Pulley When raising the flag, stand at the bottom of the flagpole and pull the rope downwards, and the flag will slowly rise. It turns out that there is a small fixed pulley with a grooved edge fixed to the top of the flagpole. You know where else...

"Exploring the Function of Pulleys" Force and Machinery PPT Courseware:

"Exploring the Function of Pulleys" Force and Machinery PPT Courseware Teaching Objectives 1. What is a fixed pulley and what is a movable pulley 2. The benefits of fixed pulleys and the benefits of movable pulleys 3. Theoretical analysis of pulleys will be carried out based on the balance conditions of levers 4. In the pulley group The relationship between tension and gravity...

File Info

Update Time: 2024-09-09

This template belongs to Physics courseware Guangdong and Shanghai version of eighth grade physics volume 2 industry PPT template

Preview