Newton's second law integration

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Homework Help Overview

The discussion revolves around the integration of Newton's second law, specifically the equation \(\frac{mdv}{F(v)} = dt\), to derive an expression for time \(t\) in terms of velocity \(v\). Participants are exploring the implications of integrating force as a function of velocity and the relationships between velocity, time, and force.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the integration process and the implications of variable substitution within the integral. Questions arise regarding the treatment of differentials and the significance of using different variable names during integration. Some express confusion about the relationship between the variables and the limits of integration.

Discussion Status

The discussion is active, with participants providing insights on the integration process and clarifying misconceptions about variable usage. Some participants have offered guidance on how to approach the integral and the interpretation of results, while others are still seeking clarity on specific steps and concepts.

Contextual Notes

Participants are working within the constraints of a homework problem that requires them to integrate and analyze motion under a force dependent on velocity. There is an emphasis on understanding the implications of constant versus variable forces and the correct application of integration techniques.

  • #31
Oblio said:
I thought we subbed F(v) out of the integral?

Yes. what do you get when you do that?
 
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  • #32
t =mF(v) \int^{v}_{vo} dv
 
  • #33
Oblio said:
t =mF(v) \int^{v}_{vo} dv

before you take out F(v), you should replace it with Fo... so what do you get when you solve for v?
 
  • #34
t= mF(o) \int^{v}_{vo} dv

t= mF(o) (v-vo)

solve for v from here?
 
  • #35
Oblio said:
t= mF(o) \int^{v}_{vo} dv

t= mF(o) (v-vo)

solve for v from here?

Yes, one thing though, it should be m/Fo because the F(v) was in the denominator not the numerator.
 
  • #36
Typo. my bad

v = F(o)t / m + V(o) ?
 
  • #37
Oblio said:
Typo. my bad

v = F(o)t / m + V(o) ?

yup.
 
  • #38
So... why is this especially significant? They want to see some kind of comment.
Something to do with velocity dependence?
 
  • #39
Oblio said:
So... why is this especially significant? They want to see some kind of comment.
Something to do with velocity dependence?

What kind of motion is it?

v = F(o)t / m + V(o)

describe the kind of motion the object is undergoing.
 
  • #40
the motion would be linear i believe
 
  • #41
Oblio said:
the motion would be linear i believe

Yes, velocity is changing linearly. What about the acceleration?
 
  • #42
YES! your back :)
um...

increasing with time?
 
  • #43
Oblio said:
YES! your back :)
um...

:)

increasing with time?

nope.
 
  • #44
also constant?
 
  • #45
Oblio said:
also constant?

yes. compare:

v = v0 + at

with

v = v0 + (Fo/m)t

the equations have the same form.
 
  • #46
O ya!
I can say both are linear then?
 
  • #47
Oblio said:
O ya!
I can say both are linear then?

Well, linear with constant acceleration. Linear just means the object moves along a straight line.
 
  • #48
Yeah, understood.
 

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