- #1
Bacat
- 151
- 1
Homework Statement
A particle of mass m moves through a medium that resists its motions with a force of magnitude
[tex]-mk(v^2+av)[/tex]
where k and a are positive constants. If no other force acts, and the particle has an initial velocity v0, find the distance traveled after a time t.
Show that the particle comes to rest as [tex]t \to \infty[/tex]
Homework Equations
[tex]F=m\frac{dv}{dt}[/tex]
The Attempt at a Solution
EOM: [tex]-k(v^2 + av) = \frac{dv}{dt}[/tex]
[tex]dt=\frac{dv}{-k(v^2+av)}[/tex]
[tex]\int \!dt=-\frac{1}{k} \int \! \frac{dv}{(v^2+av)}[/tex]...Integrate in Mathematica...
[tex]t-t_0 = \frac{Ln(a+v)-Ln(v)}{ak}[/tex]
[tex]Exp(atk)=\frac{a+v}{v}[/tex]
[tex]v(Exp(atk)-1)=a[/tex]
[tex]v(t)=\frac{a}{Exp(atk)-1}[/tex]
Set v = v0 at time t=0...
[tex]v(0) = v_0 = \frac{a}{Exp(0)-1} = \frac{a}{0}[/tex]
But this is not defined!
Did I make a mistake? How do I set v = v0 if I get infinity?
Thank you for your time and help.