What are Newton's law
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Newton's First Law:
Newton's first law, , tells us that if no other body acts on a body, it will remain indefinitely moving in a straight line with constant speed (including the state of rest, which equals zero velocity).
As we know, the movement is relative, that is, it depends on which is the observer who describes the movement. Thus, for a passenger on a train, the interventor is walking slowly down the train corridor, while for someone who sees the train passing from the platform of a station, the intervener is moving at a high speed. Therefore, a reference system is required to refer to the movement. Newton's first law serves to define a special type of reference systems known as Inertial Reference Systems, which are those reference systems from which it is observed that a body on which no net force acts moves with constant velocity.
Actually, it is impossible to find an inertial reference system, since there is always some kind of force acting on bodies, but it is always possible to find a reference system in which the problem that we are studying can be treated as if we were in a Inertial system. In many cases, assuming a fixed observer on Earth is a good approximation of the inertial system.
Newton's Second Law:
Newton's Second Law is responsible for quantifying the concept of force. It tells us that the net force applied on a body is proportional to the acceleration that the body acquires. The constant of proportionality is the mass of the body, so that we can express the relation as follows:
F = m a
Both force and acceleration are vector magnitudes, that is, they have, in addition to a value, a direction and a direction. In this way, Newton's Second Law must be expressed as:
F = m a
The unit of force in the International System is Newton and is represented by N. A Newton is the force that must be exerted on a body of one kilogram of mass to acquire an acceleration of 1 m / s2, that is,
1 N = 1 Kg · 1 m / s 2
The expression of Newton's Second Law that we have given is valid for bodies whose mass is constant. If the mass varies, such as a rocket that burns fuel, the relation F = m · a is not valid. We are going to generalize Newton's Second Law to include the case of systems in which mass can vary.
To do this we first define a new physical quantity. This physical quantity is the quantity of movement that is represented by the letter p and that is defined as the product of the mass of a body by its speed, that is to say:
P = m · v
The amount of movement is also known as the linear momentum. It is a vector magnitude and in the International System it is measured in Kg · m / s. In terms of this new physical quantity, Newton's Second Law is expressed as follows:
The Force acting on a body is equal to the temporal variation of the amount of movement of that body, that is,
F = dp / dt
In this way we also include the case of bodies whose mass is not constant. In case the mass is constant, recalling the definition of momentum and how a product is derived:
F = d (m · v) / dt = m · dv / dt + dm / dt · v
As the mass is constant
Dm / dt = 0
And remembering the definition of acceleration, we have
F = m a
As we have seen previously.
Another consequence of expressing Newton's Second Law using momentum is what is known as the conservation principle of momentum. If the total force acting on a body is zero, Newton's Second Law tells us that:
0 = dp / dt
That is, the derivative of the momentum with respect to time is zero. This means that the amount of movement must be constant over time (the derivative of a constant is zero). This is the principle of conservation of momentum: if the total force acting on a body is zero, the amount of movement of the body remains constant over time.
Newton's third law:
As we said at the beginning of Newton's Second Law, forces are the result of the action of some bodies on others.
The third law, also known as the Principle of Action and Reaction, tells us that if a body A exerts an action on another body B, it performs on another equal and opposite action.
This is something we can check daily on numerous occasions. For example, when we want to jump upwards, we push the ground to propel us. The reaction of the soil is what makes us jump up.
When we are in a pool and push someone, we also move in the opposite direction. This is due to the reaction that the other person makes about us, even if they do not try to push us.
It should be noted that, although the action and reaction pairs have the same opposite value and meanings, they do not cancel each other out, since they act on different bodies.
Newton's first law, , tells us that if no other body acts on a body, it will remain indefinitely moving in a straight line with constant speed (including the state of rest, which equals zero velocity).
As we know, the movement is relative, that is, it depends on which is the observer who describes the movement. Thus, for a passenger on a train, the interventor is walking slowly down the train corridor, while for someone who sees the train passing from the platform of a station, the intervener is moving at a high speed. Therefore, a reference system is required to refer to the movement. Newton's first law serves to define a special type of reference systems known as Inertial Reference Systems, which are those reference systems from which it is observed that a body on which no net force acts moves with constant velocity.
Actually, it is impossible to find an inertial reference system, since there is always some kind of force acting on bodies, but it is always possible to find a reference system in which the problem that we are studying can be treated as if we were in a Inertial system. In many cases, assuming a fixed observer on Earth is a good approximation of the inertial system.
Newton's Second Law:
Newton's Second Law is responsible for quantifying the concept of force. It tells us that the net force applied on a body is proportional to the acceleration that the body acquires. The constant of proportionality is the mass of the body, so that we can express the relation as follows:
F = m a
Both force and acceleration are vector magnitudes, that is, they have, in addition to a value, a direction and a direction. In this way, Newton's Second Law must be expressed as:
F = m a
The unit of force in the International System is Newton and is represented by N. A Newton is the force that must be exerted on a body of one kilogram of mass to acquire an acceleration of 1 m / s2, that is,
1 N = 1 Kg · 1 m / s 2
The expression of Newton's Second Law that we have given is valid for bodies whose mass is constant. If the mass varies, such as a rocket that burns fuel, the relation F = m · a is not valid. We are going to generalize Newton's Second Law to include the case of systems in which mass can vary.
To do this we first define a new physical quantity. This physical quantity is the quantity of movement that is represented by the letter p and that is defined as the product of the mass of a body by its speed, that is to say:
P = m · v
The amount of movement is also known as the linear momentum. It is a vector magnitude and in the International System it is measured in Kg · m / s. In terms of this new physical quantity, Newton's Second Law is expressed as follows:
The Force acting on a body is equal to the temporal variation of the amount of movement of that body, that is,
F = dp / dt
In this way we also include the case of bodies whose mass is not constant. In case the mass is constant, recalling the definition of momentum and how a product is derived:
F = d (m · v) / dt = m · dv / dt + dm / dt · v
As the mass is constant
Dm / dt = 0
And remembering the definition of acceleration, we have
F = m a
As we have seen previously.
Another consequence of expressing Newton's Second Law using momentum is what is known as the conservation principle of momentum. If the total force acting on a body is zero, Newton's Second Law tells us that:
0 = dp / dt
That is, the derivative of the momentum with respect to time is zero. This means that the amount of movement must be constant over time (the derivative of a constant is zero). This is the principle of conservation of momentum: if the total force acting on a body is zero, the amount of movement of the body remains constant over time.
Newton's third law:
As we said at the beginning of Newton's Second Law, forces are the result of the action of some bodies on others.
The third law, also known as the Principle of Action and Reaction, tells us that if a body A exerts an action on another body B, it performs on another equal and opposite action.
This is something we can check daily on numerous occasions. For example, when we want to jump upwards, we push the ground to propel us. The reaction of the soil is what makes us jump up.
When we are in a pool and push someone, we also move in the opposite direction. This is due to the reaction that the other person makes about us, even if they do not try to push us.
It should be noted that, although the action and reaction pairs have the same opposite value and meanings, they do not cancel each other out, since they act on different bodies.
Answered by
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Hi friend,
First law:
In an inertia, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
Second law:
In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object:
F = ma.
Third law:
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
F12=-F21
Hope this helps you...
Please mark it as brainliest answer...☺☺
First law:
In an inertia, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.
Second law:
In an inertial reference frame, the vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration a of the object:
F = ma.
Third law:
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
F12=-F21
Hope this helps you...
Please mark it as brainliest answer...☺☺
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