Grade 7 Science Workbook A Section 7 Newton s First Law

Workbook A: 1. Motion, Static, Motion.

2. Person A: Inertia The bus brakes suddenly, and it falls forward due to the inertia of the person.

3. Inertial friction.

4. Constant speed deceleration and acceleration.

5. Inertia. 7-13：dbccdca

14. The speed of movement to the right decreases, the speed of movement to the left increases, and the original state of movement is maintained.

We've done it before, and here's it.

Workbook A: Question 1: Movement Rest Movement state.

Question 2: Person A: Inertia The bus brakes suddenly, and the person falls forward due to inertia.

Question 3: Inertia Friction.

Question 4: Constant speed deceleration and acceleration.

5. Inertia. 7-13：dbccdca

14. The speed of movement to the right decreases, and the speed of movement to the left increases, and the inertia increases.

Is it Chapter 2, Section 7, Newton's First Law (1)?

1.No external force at rest Uniform straight line Size Direction of motion 5(1) Speed resistance (2) Smooth small far away (3) Far small slow 6(1) Simultaneous landing (2) Air resistance.

Workbook A: Question 1: Movement Rest Movement state.

Question 2: Person A: Inertia The bus brakes suddenly, and the person falls forward due to inertia.

Question 3: Inertia Friction.

Question 4: Constant speed deceleration and acceleration.

5. Inertia. 7-13：dbccdca

14. The speed of movement to the right decreases, and the speed of movement to the left increases, and the inertia increases.

Hey, thank you so much

On April 29, 2009, the Chongqing Chaotianmen Yangtze River Bridge, which has set a number of world firsts, was officially opened. The main bridge of the bridge is 932m long, and the permanent steel consumption of the whole bridge has reached a record in China.

1) Is the permanent steel of the bridge subject to gravity? (take g=10n kg).

2) If the pedestrian crossing the bridge from the bridge to the pedestrian crossing the bridge is walking at a speed, how long does it take him to cross the main bridge? (The result is a whole number).

1. Newton's First Law.

Contents: When all objects are not affected by external forces, they always maintain a uniform linear motion or a stationary state.

Emphasis: "everything" indicates the general applicability of this law, there are no exceptions, and objects that do not conform to this law do not exist; "Not being subjected to external forces" is a condition for this law to be true, it is an ideal situation, and it also includes the case where an object is not affected by an external force in a certain direction. "Total hold" means that when the object is not subject to external force, there are only two possibilities: to maintain stationary or uniform linear motion, and to change this state, the object must be affected by force.

When the object is not affected by external forces, the original moving object should maintain a uniform linear motion; The law that a stationary object should remain at rest shows that no force is required to maintain the uniform linear motion of the object. (i.e., the force is not the cause that maintains the motion of the object or the force is the cause of changing the motion of the object.)

Newton's first law is not derived directly from experiments, but it has a deep experimental foundation. It is obtained through further scientific reasoning on the basis of experiments, and all scientific inferences further derived from this law have withstood the test of practice, so Newton's first law has long become one of the recognized fundamental laws of mechanics.

1.Conditions for the balance of two forces: ......

2.Application of the two-force equilibrium condition: To solve the problem by applying the two-force equilibrium condition, it is first necessary to determine whether the object under study is in a state of stationary or uniform linear motion, and only when the object is in a state of rest or uniform linear motion can this condition be applied.

For an object to which the two-force equilibrium condition can be applied, it is necessary to analyze how many forces it is subjected to, and in what direction. For example, when the trailer is lit and burned on the horizontal plane and moves in a uniform linear line, the two forces in the vertical direction are balanced, and the two forces in the horizontal direction are also balanced. In the course of student analysis, attention should be paid to correcting the simplification and one-sidedness of students' understanding.

Any object remains at rest or in a uniform linear motion until it is forced to change this state by the forces of other objects.

Explanation: Objects have a tendency to maintain rest and move in a uniform linear line, so the motion state of the object is determined by its motion speed, and its motion state will not change without external force. This property of an object is called inertia.

So Newton's first law is also known as the law of inertia. The first law also clarifies the concept of force. It is clarified that force is the interaction between objects, and it is pointed out that it is force that changes the motion state of objects.

Because acceleration describes the change in the state of motion of an object, force is related to acceleration, not to velocity. If you don't pay attention to this in your daily life, you will often have a false impression.

Note: Newton's first law does not hold true in all frames of reference, in fact it only holds in inertial frames of reference. Therefore, Newton's first law is often used as a criterion for whether the frame of reference is an inertial frame of reference.

Analysis: There is no contradiction at all. It just shows the correctness of Newton's first law.

Newton's first law of motion, also known as the law of inertia, states that any object always maintains a uniform linear motion or a state of rest when it is not subjected to any force or the combined external force is zero, until an external force acting on it forces it to change this state.

Braking is to change the motion of an object. At this time, it is more difficult for the object with a large mass to move in a state of motion, so when the speed is small, the light box is easy to change the state of motion, so it is easy to slide when braking, and conversely, it is not easy for a heavy object to change the state of motion.

That is, the mass of an object is a measure of the size of inertia.

I don't think that's possible, if they have the same coefficient of friction, the two boxes should be in the same motion.

Not contradictory! Because the motion of an object is affected by the "external force" and its own "inertia", the force has to change its state of motion (let the box stop with the car and not let it slide), and the inertia has to maintain its state of motion (let the box still move, that is, slide on the car), whoever has the greatest effect will eventually achieve the effect! In the three cases, the inertia and friction of the two boxes remain the same, and the speed of movement increases in turn, the better the motion state is maintained, and the more difficult it is to change!

So the above situation arises!

According to Newton's first law:

Any object that is not subject to any external force always maintains a state of uniform linear motion or a state of rest, until an external force forces it to change this state.

There is no force exerted on the object, and Li Fengqiao is not affected by any external force or key, so the velocity and direction of the object do not change.

The answer is d

1. Newton's first law says that when the combined external force on an object is zero, the object is in a state of static clump or uniform linear motion. The object removes all the external forces, and the net force remains zero, so it is at rest.

2. The external force of selling Changhe is not zero, and the state of movement must change. Or a change in speed, or a change in direction.

Study hard You are a top student 3102

Analysis: The content of Newton's first law: all objects always remain at rest or in a state of uniform linear motion when they are not subjected to any force

Inertia: Objects always have the property of keeping their original state of motion unchanged, this property is called inertia All objects have inertia

It is the reason for changing the state of motion of the object

A: Anyway, you've chosen it, so I won't talk about it.

On the earth, when a single pendulum swings to the other side, gravity and the pull of the line will synthesize a recovering force to cause the single pendulum to swing back and forth, but in space, this g does not exist, and the force of the rope acts as a centripetal force perpendicular to the direction of motion of the ball, so there is no force in the distance of the ball's motion, only an initial velocity given at the beginning of the push-out, so the single pendulum moves in a circular motion.