The position vector r of a particle in an xy plane is given by r=(2t^3-5t)i+(6-7t^4), with vector r in meters and t in seconds. In unit vector notation calculate r? I'm completely lost how to get the unit vector where there is no t variable because we're not given t or anything. Please help.

Question

roadjester · Answer

one sec while I write it out

vincent-lyon.fr · Answer

What is meant by "unit vector notation" ?
Is it another name for polar coordinates?

roadjester · Answer

a unit vector is a vector whose length is 1

roadjester · Answer

@Vincent-Lyon.Fr 
are you familiar with i, j, and k to represent x, y, and z respectively

vincent-lyon.fr · Answer

Yes I am, but I am puzzled because 
 r=(2t^3-5t)i+(6-7t^4)j

is already resolved along i and j. (both unit vectors)

What I do not understand, is what kind of r = ...??...  type or formula is expected here.

roadjester · Answer

actually, i didn't see a j...

anonymous · Answer

yea unit vector would just be like r=xi+yj the answer in the back is r= 6m i - 106m j

roadjester · Answer

could you write out the whole question? or is that it?

anonymous · Answer

oh and I meant for there to be a j originally

anonymous · Answer

and that's the whole question for part a at least

roadjester · Answer

ok, can you write the WHOLE question? all parts?

vincent-lyon.fr · Answer

They must give you the value of t somewhere in the question.

roadjester · Answer

maybe there's some information that is provided in the other parts
also, i think I recognize that question, is your book by any chance Serway-Jewett, physics for scientists and engineers?

anonymous · Answer

That's what I'm confused about is that there is no t given like in the example at the beginning of the chapter, and it says it's supposed to be an easy problem... And it's actually Fundamentals of Physics by Jearl Walker

roadjester · Answer

Regardless, please type out the full question including parts b, c, etc
Perhaps we may see something that you missed

anonymous · Answer

The position vector r of a moving particle in an xy plane is given by vector r=(2t^3-5t)i+(6-7t^4)j, with vector r in meters and t in seconds. In unit-vector notation, calculate a)vector r, b) vector v (velocity), c) vector a (acceleration) for t=2.0s

anonymous · Answer

ok I think I just should have read all the way through cuz they gave t

roadjester · Answer

t=2

roadjester · Answer

:)

anonymous · Answer

wellp I guess I can get on with my homework now, thanks!