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jayeshtrivedi
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Can we say that the First law of Newton defines the force whereas the Second law gives the magnitude of force?
jayeshtrivedi said:Can we say that the First law of Newton defines the force whereas the Second law gives the magnitude of force?
Are you sure? First Newton's law concludes from the second Newton's law (you also have to assume that if force is not acting then F=0). Therefor the first Newton's law is not needed to define force.DrStupid said:All three laws together define force.
olgerm said:Are you sure? First Newton's law concludes from the second Newton's law (you also have to assume that if force is not acting then F=0). Therefor the first Newton's law is not needed to define force.
##a=\frac{F}{m} \to \frac{\partial v}{\partial t}=\frac{F}{m}##⇒change of velocity(motion) is proportional to force.DrStupid said:According to the first law force is the reason for changes of motion. This causality doesn't follow from the second law.
olgerm said:##a=\frac{F}{m} \to \frac{\partial v}{\partial t}=\frac{F}{m}##⇒change of velocity(motion) is proportional to force.
I agree. Newton's II law only defines netforce.pixel said:Newton's laws involve the effect of an unbalanced (net) force on rest or motion. I don't think they define force.
Netforce is change of momentum per timeunit.yrjosmiel said:Force is basically the change of momentum per second.
Or to be more exact, that.olgerm said:Net force is change of momentum per time unit.
olgerm said:Netforce is change of momentum per timeunit.
It seems that force is proportional to velocity with : ∫ F dx = ∫xxo mv dv/dx (dx) = ∫vv0 mvdv = 1/2mv2 - 1/2mv02 , Δ KE ≅ v - v0DrStupid said:That just means that force is a measure for the change of motion. It doesn't mean that force is the reason for the change of motion as the first law says.
PS: Motion means momentum and not velocity. Newtons term for momentum is "motus" and his term for velocity is "velocitate". In the second law he used the term "motus". That means that force is proportional to the change of momentum but not necessarily to the change of velocity.
morrobay said:It seems that force is proportional to velocity with : ∫ F dx = ∫xxo mv dv/dx (dx) = ∫vv0 mvdv = 1/2mv2 - 1/2mv02 , Δ KE ≅ v - v0
As opposed to ∫tt0 F dt = t∫t0 m dv/dt = ∫t0t d/dt mv = dp/dt
F ≅ t - t0
Does this statement contain any information, that equation ##\frac{\partial^2 x}{\partial t^2}=\frac{F_x}{m}## doesn't?DrStupid said:force is the reason for the change of motion as the first law says.
And also with ∫ F dtmorrobay said:It seems that force is proportional to velocity with : ∫ F dx = ∫xxo mv dv/dx (dx) = ∫vv0 mvdv = 1/2mv2 - 1/2mv02 , Δ KE ≅ v - v0
olgerm said:Does this statement contain any information, that equation ##\frac{\partial^2 x}{\partial t^2}=\frac{F_x}{m}## doesn't?
I doubt that this statement is even meaningful. Could any experiment prove that? Newton's 1st law as worded in Wikipedia ("In an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.") does not say anything about causality.DrStupid said:it contains information about causality: According to the first law F is the cause for the effect d²x/dt².
?Wikipedia said:Causality should not be confused with Newton's second law, which is related to the conservation of momentum, and is a consequence of the spatial homogeneity of physical laws. The name causality suggests that all effects must have specific causes, which is a concept unrelated to the common use of causality in physics, and is violated in some mainstream interpretations of quantum mechanics.
olgerm said:Could any experiment prove that?
olgerm said:Newton's 1st law as worded in Wikipedia ("In an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.") does not say anything about causality.
jayeshtrivedi said:Can we say that the First law of Newton defines the force whereas the Second law gives the magnitude of force?
First Newton's Law, also known as the Law of Inertia, states that an object will remain at rest or in motion at a constant velocity unless acted upon by an external force. Second Newton's Law, also known as the Law of Acceleration, states that the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass.
First and Second Newton's Law are closely related, as the Law of Inertia is a special case of the Law of Acceleration. This means that the Law of Inertia can be derived from the Law of Acceleration by setting the net force to be equal to zero.
The formula for Second Newton's Law is F=ma, where F represents the net force acting on an object, m represents the mass of the object, and a represents the acceleration of the object.
Yes, Second Newton's Law can be applied to objects with variable mass. In this case, the mass in the formula is the instantaneous mass at a given time, which can change as the object moves.
First and Second Newton's Law have many real-life applications, such as understanding the motion of objects in everyday life, designing vehicles and structures, predicting the motion of celestial bodies, and developing technologies like rockets and airplanes.