(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A freight car of mass M contains a mass of sand m. At t=0, a constant horizontal force F is applied in the direction of rolling and at the same time a port in the bottom is opened to et the sand flow out at tconstant rate dm/dt. Find the speed of the freight car when all the sand is gone. Assume the car is at rest t=0

3. The attempt at a solution

[tex]P_t=Mv(t)+{m_0}-t{{dm}\over{dt}}[/tex]

I was trying to solve [tex]m_0-t(dm/dt)=0[/tex]

such that I know the t when all the sand is gone

but I can't solve it.

as it turns out to be

[tex]\int {{dt}\over{t}}=\int {{dm}\over{m_0}}[/tex]

it doesn't make sense at all when t=o! (undefined for In0)

also, the equation of the momentum still has two unknowns for one equation, (even I take dp/dt, I still not sure about d^2/dt(x))

Thanks for your reading!

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# Homework Help: A Mass flow car

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