I have a trouble with this problem:(adsbygoogle = window.adsbygoogle || []).push({});

Suppose you have a particle with mass 30Kg, this particle is in influence of a force F that acts along the x axis and F=6+4x-3(x^2) and at x=0 the particle has 0m/s speed. Find the total work made by F between x=0 and x=3, then find the power given to the particle when x=3. (answers= 9 Joules and 22 Watts)

Well the first thing is easy, only I have to integrate F between 0 and 3. but the second question I can't see what's to be done. I try to use the fact that if I have the work I must get the final time but I don't have an expression for the trayectory.

Another way I have tried is to get the function of position by the fact that

F=ma, a=F/m dv/dt=(6+4x-3(x^2))/m

this is a partial differential equation involving the second derivative of a function u(x,t) and the general solution I get is:

u(x,t)=a(x)+b(x)t+(t^2)((6+4x-3(x^2))/2m)

but I don't have the sufficient conditions to get a good boundary problem or initial problem to separate a particular solution.

My questions are: what conditions could I put, or what other way, easier, could I take to solve this?

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# Homework Help: Interesting and annoying power problem

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