- #1
uber_kim
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Homework Statement
I'm having problems with some differential equations, just need to know where I'm going wrong.
Homework Equations
The Attempt at a Solution
a) mv[itex]\stackrel{dv}{dx}[/itex]=F(x)
mvdv=F(x)dx
m∫vdv=∫F(x)dx
v^2=v[itex]v^{2}_{0}[/itex]+[itex]\stackrel{2}{m}[/itex]∫F(x)dx
Setting F(x)=-kx
v^2=[itex]v^{2}_{0}[/itex]-[itex]\stackrel{k}{m}[/itex](x^2-[itex]x^{2}_{0}[/itex])
I then have to find the position as a function of time..
[itex]\stackrel{dx}{dt}[/itex]=[itex]\sqrt{v^{2}_{0}-\stackrel{k}{m}(x^2-x^{2}_{0}}[/itex]
dx/[itex]\sqrt{v^{2}_{0}-\stackrel{k}{m}(x^2-x^{2}_{0}}[/itex]=dt
I'm not sure how to do that integral, though, or if that's even right.
b) This problem involves a disc moving along a rough surface, so it has friction (F) and linear air resistance (-bv) acting on it.
ma=-bv+F
mdv/dt=-bv+F
-[itex]\stackrel{m}{b}[/itex]∫dv/v=∫Fdt
-[itex]\stackrel{m}{b}[/itex]ln([itex]\stackrel{v}{v_0}[/itex]=Ft
e^(-[itex]\stackrel{m}{b}[/itex])v/v_o=e^(Ft)
v=v_0e^(-Fbt/m)
Thanks for any help!