Any object must maintain a uniform linear motion or a static state until an external force forces it to change its motion state. Expressed by mathematical formula as:

These include:

It is the resultant force, v is the speed, and t is the time.

2, Newton's second law of motion:

The acceleration of an object is directly proportional to the acting force, inversely proportional to the mass of the object and directly proportional to the reciprocal of the mass of the object; The direction of acceleration is the same as that of acting force.

Expressed by an equation, that is, F=kma, where k is the proportional coefficient; Only when f is Newton, m is kilogram and a is m/s? When it is a unit, F=ma holds.

3, Newton's third law of motion:

The acting force and reaction force between two interacting objects are always equal in size and opposite in direction, and act on the same straight line.

The expression formula is:

1687, the British physicist isaac newton put forward Newton's laws of motion in his masterpiece Mathematical Principles of Natural Philosophy, and Newton's first law of motion was one of them? . Newton's first law and Newton's second and third laws constitute a complete system of Newtonian mechanics. Newton's first law gives the concept of inertial system, while the particle mechanics system established by the second and third laws and Newton's law of motion is only valid for inertial system. Therefore, Newton's first law is indispensable and an important mechanical law that is completely independent.

Extended data:

1, scope of application of Newton's first law of motion:

Newton's first law only applies to inertial reference frames. When a particle is not affected by external force, the reference frame that can judge whether the particle is stationary or moving in a straight line at a constant speed must be the inertial reference frame, so Newton's first law of motion is only applicable in the inertial reference frame.

2, the scope of application of Newton's second law of motion:

Newton's second law of motion only applies to particles. For particle systems, the isolation method generally adopts Newton's second law of motion or Newton's second law of particle systems. Newton's second law of motion only applies to inertial reference frames. Inertial frame of reference refers to the frame of reference in which Newton's law of motion is established, and Newton's second law of motion is not applicable in non-inertial frame of reference. However, through the introduction of inertial force. The expression of Newton's second law of motion can be used in non-inertial system.

3, the scope of application of Newton's third law of motion:

Newton's third law of motion only applies to the interaction between physical objects in inertial system. For example, electrons moving in an electromagnetic field will be subjected to electromagnetic force, but the reaction of electrons to the electromagnetic field is out of the question. Inertia force in non-inertial system has no reaction force; The interaction involving field needs time to transmit its action, and the simultaneity of action and reaction is not established. The third law is independent, but it also has its scope of application.

References:

Baidu encyclopedia-Newton's first law of motion

References:

Baidu Encyclopedia-Newton's Second Law of Motion

References:

Baidu Encyclopedia-Newton's Third Law