"Description of Motion" Mechanical Motion PPT Courseware 3

Description

"Description of Motion" Mechanical Motion PPT Courseware 3

learning target

Do you know what mechanical motion is? Know that motion is a universal phenomenon in the universe.

Know the relationship between the reference object and the movement of the object. Be able to select the reference object correctly.

Know the relativity between motion and rest.

Movement is a common phenomenon in nature

In addition to mechanical movement, there are many forms of movement, such as the movement of molecules and atoms in the microscopic world, electromagnetic movement, and the vibrant movement of life...

mechanical movement

Definition: Changes in the position of an object are called mechanical motion.

Changes in location include:

A. Change in distance relative to an object.

B. Change in orientation relative to an object.

Why do different people make different judgments about the motion and stillness of the same object?

The objects selected as standards are different

Reference object

1. Reference object: When studying the motion of an object, another object selected as the standard is called the reference object.

①The reference object is an object that is assumed to be motionless. You can choose arbitrarily (both moving and stationary objects can be used as reference objects)

②Once the reference object is selected, we assume that the object is stationary.

③The research object cannot be used as a reference

④When studying the movement of objects on the ground, the ground or fixed objects on the ground are often used as reference objects. Therefore, in physics, the ground or a stationary object on the ground is generally selected as the reference object.

⑤It is meaningless to say whether an object is moving or stationary without reference. Because the motion state of the same object is different relative to different reference objects.

2. The relativity between motion and stillness

Whether the same object is in motion or at rest depends on the chosen reference object.

3. Relatively still

Objects moving at the same speed and in the same direction are at rest relative to each other. That is, one of them is used as a reference and the other is stationary.

Do it

Put the textbook on the desk, then put the pencil case on the textbook, slowly pull the textbook with your hands, observe and think:

1. If the desk is used as a reference object, is the pencil box moving or stationary?

2. If the textbook is used as a reference object, is the pencil box moving or stationary?

Determine whether an object is moving or stationary

Take a look at which object to choose as a reference.

Second, see if there is a position change between the object to be judged and the reference object. If there is a position change, then the object to be judged is moving; if there is no position change, then the object to be judged is stationary.

Can you judge the reference object selected in the question?

1. "The sun rises in the east and sets in the west." The movement of the sun is based on ______

2. "The moon passes through the clouds", the movement of the moon is based on _____

3. Passengers sit quietly in a running train. The movement of the train is based on _____

Practice in class:

Please judge the motion and rest of an object?

1. For passengers sitting in a bamboo raft floating along the river, if the river bank is used as a reference, the bamboo raft is _____; and if the flowing water is used as a reference, the bamboo raft is ___ __.

2. Geostationary communication satellites are _____ relative to the earth, and relative to the sun.

3． Two cars are traveling in the same direction. The movement of the cars is described using ________ as a reference. A passenger sitting in car A sees car B moving backwards. The passenger uses ________ as a reference. Comparing the two cars, the ________ car drives faster.

4. Which of the following statements is correct: ( )

A. A car passes over a bridge. The car is moving but the bridge is absolutely stationary.

B. The universe is composed of moving objects, absolutely motionless objects do not exist

C. The earth and planets all move around the sun, and the sun is absolutely motionless in the universe.

D． After a house is built, it is fixed in its original position and will not move, so objects fixed on the earth are absolutely immovable.

Class summary

1. Mechanical motion: In physics, changes in the position of an object are called mechanical motion.

2. Reference object: Whether an object is moving or stationary depends on which object is used as the standard. The object chosen as the standard is called the reference object

Determine whether an object is moving or stationary

Take a look at which object to choose as a reference.

Second, check whether there is a change in position between the object being judged and the reference object.

3. Movement is a common phenomenon in the universe. The motion and rest of an object are relative.

Enrich your notes

The relativity between object movement and rest includes three levels of meaning:

1. Movement is absolute, and all objects are in motion.

2. Stillness is relative.

3. The movement of objects is relative. Depending on the reference object selected, the moving and stationary situations are different.

In short: it is impossible to determine whether an object is moving or stationary without selecting a reference object in advance. When we usually talk about movement and stillness, the ground is used as a reference. At this time, we generally do not specify what the reference is.

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Update Time: 2024-11-05

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 1 industry PPT template

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