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

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"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. Advantages of fixed pulleys and advantages of movable pulleys

3. Will conduct a theoretical analysis of the pulley based on the balance conditions of the lever.

4. The relationship between tension and gravity in the pulley block

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.

Using a fixed pulley is neither labor-saving nor labor-intensive, but it can change the direction of the force. s=h, F=G．

Using a movable pulley can save half the force, but it takes twice the distance and does not change the direction of the force. S=2h, F=G/2．

fixed pulley

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: When friction is not considered, the pulling force is equal to the gravity of the heavy object. (F＝G)

3: The direction of the pulling force is opposite to the direction of movement of the weight.

Conclusion: Using a fixed pulley does not save ＿＿, but it can change the ＿＿ of the applied force.

moving pulley

A: The fulcrum is at edge O

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

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

2: In the above case, the power is 1/2 of the resistance

That is, F=1/2 G

3: The direction of the pulling force is the same as the moving direction of the weight.

Conclusion: Using a movable pulley can ＿＿, but it cannot change the ＿＿ of the applied force.

Ability testing

1 As shown in the figure, write the relationship between F and G (friction and the dead weight of the movable pulley are not included): F1=____G, F2=____G.

2 As shown in the figure, when F pulls the object upwards and rises 10cm, the object rises ______cm. If the pulley weight and friction are not included, then F =______G.

Consolidation exercises:

1: As shown in the figure (a) below, 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 the figure (b) above, 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)

3: Among the four pulley sets shown in the figure, figure __________ can save half the effort, figure __________ is the most laborious, and figure __________ and figure __________ require the same amount of force.

Operation

P36 pages 1, 2, 3,

Tutorial (preview):

1. Review Chapter 6

2. What is motion and stillness?

3. What is a reference object?

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

"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? Use the pulley..

"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...

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Update Time: 2024-11-22

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

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