"Pulley" Simple Machine Function PPT Courseware

Description

"Pulley" Simple Machine Function PPT Courseware

learning target

(1) Understand fixed pulleys and movable pulleys;

(2) Understand the structure and characteristics of fixed pulleys and movable pulleys;

(3) Understand the structure of the pulley block;

(4) Know the relationship between the pulling force in the pulley block and the gravity of the lifted object.

pulley

Observe the characteristics of the machinery in the picture and try to summarize the concept of pulleys.

A pulley is a small wheel with grooves around it that can rotate around an axis.

1. Fixed pulley and movable pulley

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

Observation and Experimentation

Observe the use of pulleys

Experimental steps

(1) Install the fixed pulley and movable pulley as shown in the figure

(2) Measure the relevant data when using a spring dynamometer to directly lift the hook code, and using a fixed pulley and a movable pulley to lift the hook code respectively, and complete the following table.

Analyze the experimental data and think about the following questions:

1. Is it labor-saving (or labor-intensive) to use fixed pulleys and movable pulleys?

2. Does using fixed pulleys or movable pulleys save distance (or does it require moving a larger distance)?

3. When lifting heavy objects, what kind of pulley can be used to change the direction of force?

4. Under what circumstances is it appropriate to use fixed pulleys, and under what circumstances is it appropriate to use movable pulleys?

Experimental results

Using a fixed pulley cannot save effort or distance, but it can change the direction of the force; using a movable pulley can save effort, but it has to move a greater distance and cannot change the direction of the force.

2. Pulley block

Want to discuss

Using a fixed pulley is not labor-saving, but it can change the direction of force.

Using a movable pulley can save effort, but it cannot change the direction of force.

How can I do this in order to combine the best of both worlds? Is this possible?

Installation of pulley block

1. Combine the fixed pulley and the movable pulley into a pulley block.

2. Change the number of hook codes, measure the tension F of the spring dynamometer and the hook code weight G, and complete the following table.

Summary of this lesson

What did you gain from studying this class?

1. Fixed pulley and movable pulley

(1) Fixed pulley: When using a pulley, the pulley whose axis is fixed is called a fixed pulley. (Not effort-saving, but can change the direction of force)

(2) Moving pulley: When using a pulley, the pulley whose axis moves with the object is called a moving pulley. (Effort-saving, but the direction of force cannot be changed)

2. Pulley block

The device that combines the fixed pulley and the movable pulley is called a pulley block. (It can not only save effort, but also change the direction of force)

When using a pulley block to lift a heavy object, if the weight of the movable pulley and friction are not taken into account, and the movable pulley is lifted by several strands of rope, the force exerted will be a fraction of the weight of the object.

Practice in class

1. Use the device shown in the figure to lift the weight G at a constant speed. Among the pulling forces, force ( )

A.F1 is the largest B.F2 is the largest

C.F3 is the largest D.Same size

2. As shown in the figure, the weight of the rope and pulley is not included, and the object is in a stationary state. If M1=5kg, then M2 should be equal to ________ kg

3. As shown in the figure, three pulleys are used to pull the same object, and it moves in a straight line at a uniform speed along the same horizontal plane. The pulling forces used are F1, F2, and F3 respectively. Comparing their sizes should be ( )

A.F1＞F2＞F3 B.F1＜F2＜F3

C.F2＞F1＞F3 D.F2＜F1＜F3

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For more information about the PPT courseware "Simple Mechanical Work of a Pulley", please click on the PPT tab of "Simple Mechanical Work of a Pulley".

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Update Time: 2024-10-04

This template belongs to Physics courseware Lu Jiao Edition Eighth Grade Physics Volume 2 industry PPT template

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