Position vectors

**kithy** · September 13th 2008, 01:56 PM

I am having trouble solving this problem, can anyone help me out...please!

A particle traveling in a straight line is located at the point (1, -1, 2) and has speed 2 at time t=0. The particle moves toward the point (3, 0, 3) with constant acceleration 2i+j+k. Find its position vector r(t) at time t.

any help is greatly appreciated
thank you

**espen180** · September 13th 2008, 02:20 PM

It would be easier if you specified what part of the problem you found difficult. I'm going to assume it is the accelleration vector.

What if I tell you that

$\vec{a}(t)=\frac{d\vec{v}}{dt}=\frac{d^2\vec{p}}{d t^2}$ If you don't know, $\frac{d^2\vec{p}}{dt^2}$ is the second derivative of $\vec{p}(t)$ .
Then, $\vec{p}(t)=p_1i+p_2j+p_3k \, \Rightarrow \, \vec{v}(t)=\frac{dp_1}{dt}i+\frac{dp_2}{dt}j+\frac {dp_3}{dt}k$

or something like that, and so on.

Was that understandable?

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