Question

define newtons second law.​

Answer 1

Answer:

The second law states that the rate of change of momentum of an object is directly proportional to the force applied, or, for an object with constant mass, that the net force on an object is equal to the mass of that object multiplied by the acceleration.

Answer 2

Answer:

Newton's second law

The second law states that the rate of change of momentum of a body over time is directly proportional to the force applied, and occurs in the same direction as the applied force.

$\sf {\displaystyle \mathbf {F} ={\frac {\mathrm {d} \mathbf {p} }{\mathrm {d} t}}}$

where {\displaystyle \mathbf {p} }p is the momentum of the body.

Some textbooks use Newton's second law as a definition of force, but this has been disparaged in other textbooks.

Constant Mass

For objects and systems with constant mass, the second law can be re-stated in terms of an object's acceleration.

$\sf {\displaystyle \mathbf {F} ={\frac {\mathrm {d} (m\mathbf {v} )}{\mathrm {d} t}}=m\,{\frac {\,\mathrm {d} \mathbf {v} \,}{\mathrm {d} t}}=m\mathbf {a} ,}$

where F is the net force applied, m is the mass of the body, and a is the body's acceleration. Thus, the net force applied to a body produces a proportional acceleration.

Variable-mass systems

Main article: Variable-mass system

Variable-mass systems, like a rocket burning fuel and ejecting spent gases, are not closed and cannot be directly treated by making mass a function of time in the second law; The equation of motion for a body whose mass m varies with time by either ejecting or accreting mass is obtained by applying the second law to the entire, constant-mass system consisting of the body and its ejected or accreted mass; the result is[10]

$\sf {\displaystyle \mathbf {F} +\mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}=m{\mathrm {d} \mathbf {v} \over \mathrm {d} t}}$

where u is the exhaust velocity of the escaping or incoming mass relative to the body. From this equation one can derive the equation of motion for a varying mass system, for example, the Tsiolkovsky rocket equation.

Under some conventions, the quantity$\sf {\displaystyle \mathbf {u} {\frac {\mathrm {d} m}{\mathrm {d} t}}}$

on the left-hand side, which represents the advection of momentum, is defined as a force (the force exerted on the body by the changing mass, such as rocket exhaust) and is included in the quantity F. Then, by substituting the definition of acceleration, the equation becomes F = ma.

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