"Friction" Motion and Force PPT Courseware 2

Description

"Friction" Motion and Force PPT Courseware 2

"Beijing Daily" reported this news: A middle-aged man slipped on a watermelon rind while running and was sent to the hospital for emergency treatment. He had no pulse. A piece of watermelon rind killed a person. What a misfortune! So, what exactly caused this sudden disaster?

Why does a football rolling on the ground eventually stop?

Why do vehicle tires have uneven patterns?

Why are there wheels on the bottom of suitcases?

Why is it easy to open a rusty lock after placing some broken lead core?

small experiment

When we use different sizes of force to push a book on a horizontal table:

(1) At the beginning, you exerted a push on the book, but the book was not pushed. What does this mean?

(2) When the pushing force increases to a certain extent, the book will slide on the table. After the book slides, do you feel that pushing is still needed? What does this mean?

analyze

1. When an object is about to move, the contact surface will hinder the movement of the object. This force is called static friction.

2. When an object is sliding (or rolling), the contact surface will also hinder the movement of the object. This force is called sliding (or rolling) friction.

3. The force on the contact surface that hinders the movement of an object is collectively called friction.

Explore: What does the size of friction depend on?

Question: What does the magnitude of friction depend on?

Conjecture: 1. The pressure on the contact surface

2. Roughness of the contact surface

3.…

Basis: When you push a box, the heavier the box, the harder it is to push; the rougher the ground, the harder it is to push.

Principle: The conditions for the balance of two forces.

Equipment: spring dynamometer, weights, wooden blocks, long wooden boards

Experiment: Conduct the experiment in 12 groups, lasting 15 minutes, and record the experimental data in each group.

6. Evaluation:

(1) When using the experimental device shown in Figure A to measure the friction between the wooden block and the long wooden board, it was found that it was difficult to keep the spring dynamometer indication stable and difficult to read. Please analyze the reason?

(2) In order to solve the above problems, a student improved the experimental device, as shown in Figure B. Please describe how this device is used to measure the friction between a block of wood and a long plank.

(3) Why can the above problems be solved when using the experimental device shown in Figure B for experiments?

Example 1. As shown in the figure, two wooden blocks A and B are stacked on a horizontal surface.

(1) Apply a horizontal pulling force F=20N to object B. They are both stationary. Analyze the magnitude and direction of the friction force on objects A and B respectively.

(2) If a force acts on object A and they remain stationary, analyze the magnitude and direction of the friction force on objects A and B respectively.

Example 2: A person holds a trophy with his hand (the trophy is always in the vertical direction as shown in the picture). Which of the following statements is correct ( )

A. If the trophy is heavier, the hand needs to be held tighter

B. The tighter your hand is, the greater the friction will be on the trophy.

C. No matter how tightly you hold it, as long as it doesn't fall, the friction force on the trophy will be constant.

D. None of the above statements are correct

Example 3. As shown in the figure, a car is on a straight road with a wooden box on the car. Try to determine the friction force on the wooden box in the following situations:

① When the car accelerates from a standstill and there is no relative sliding between the wooden box and the car surface, the direction of the friction force on the wooden box is ________;

②When the car moves at a constant speed (there is no relative sliding between the two), the friction force on the wooden box is ________.

③When the car brakes and the wooden box slides forward on the car, the direction of the friction force on the wooden box is _________.

Explore and experience

5. Explore: Is the friction force related to the contact area?

1. Place the wooden block flat on the wooden board, use a spring dynamometer to pull the wooden block to move at a constant speed, and read the pulling force at this time as F1

2. Place the wooden block sideways on the wooden board, use a spring dynamometer to pull the wooden block to move at a constant speed, and read the pulling force at this time as F2

3. Place the wooden block vertically on the wooden board, use a spring dynamometer to pull the wooden block to move at a constant speed, and read the pulling force at this time as F3

4. Compare the sizes of F1, F2, and F3. If they are equal, it is irrelevant; if they are not equal, it is relevant.

Keywords: Motion and force teaching courseware, Friction force teaching courseware, New People's Education Edition eighth grade physics PPT courseware volume 2, Eighth grade physics slide courseware download, Motion and force PPT courseware download, Friction force PPT courseware download, .ppt format

For more information about the "Friction Motion and Force" PPT courseware, please click the Friction ppt motion and force ppt tag.

"Friction" interaction PPT download:

"Friction" Interaction PPT Download Part One Content: [Learning Literacy and Objectives] Physical concepts: 1. Understand the conditions and directions of sliding friction and the factors that affect its magnitude, and master the formula for calculating sliding friction. 2. Understand Conditions for the generation of static friction..

"Friction" interaction PPT courseware:

"Friction" Interaction PPT Courseware Part One: Course Standard Requirements 1. Know the conditions under which sliding friction occurs, and be able to determine its direction and solve for its magnitude..

"Friction" interaction PPT:

"Friction" Interaction PPT Part One Content: Learning Objectives 1. Know the conditions under which sliding friction occurs, and be able to determine its direction and solve for the magnitude of sliding friction. 2. Knowing the conditions under which static friction occurs, you can determine its direction and solve for the magnitude of static friction.

File Info

Update Time: 2024-10-13

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 2 industry PPT template

Preview