Differential Equation Involving Newtons Law of Motion

SparkyEng
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Homework Statement



mv'=-gm-kv

Find the position function using the initial coniditions of t=0 for all Constants

Homework Equations


Reverse product rule



The Attempt at a Solution



My attempt is on my white board. Its attached as a picture.
 

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SparkyEng said:

Homework Statement



mv'=-gm-kv

Find the position function using the initial coniditions of t=0 for all Constants

Homework Equations


Reverse product rule



The Attempt at a Solution



My attempt is on my white board. Its attached as a picture.

You've got some problems there. For example the integral of vdt isn't equal to v*t. v is a function of t. Why don't you try to solve mv'=-gm-kv using separation of variables?
 
From mv'= m dv/dt= -gm- kv, you can get m dv/(gm+kv)= -dt, separating the variables "v" and "t". Integrate both sides of that.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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