How do I find the unit tangent to the trajectory as a function of time?

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SUMMARY

The unit tangent vector for the trajectory defined by the position vector r(t) = (5*t^2)*i + (3*t^2)*j − (5*t)*k is calculated using the formula T(t) = r'(t) / |r'(t)|. The derivative r'(t) is found to be (10*t)*i + (6*t)*j - 5*k, and its magnitude is |r'(t)| = sqrt(136*t^2 + 25). The correct unit tangent vector is thus (10*t*i + 6*t*j - 5*k) / (sqrt(136*t^2 + 25)).

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Kris1
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A particle moves such that its position vector, as a function of time is
r(t) = (5*t^2)*i + (3*t^2)*j − (5*t)*k

Im trying to find the unit tangent to the trajectory as a function of time. However I can't seem to find any formula of how to do this.

Can someone please help me with a formula or as to how to go about this?
 
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Kris said:
A particle moves such that its position vector, as a function of time is
r(t) = (5*t^2)*i + (3*t^2)*j − (5*t)*k

Im trying to find the unit tangent to the trajectory as a function of time. However I can't seem to find any formula of how to do this.

Can someone please help me with a formula or as to how to go about this?

The unit tangent vector is defined to be
\[\mathbf{T}(t)=\frac{\mathbf{r}^{\prime}(t)} {|\mathbf{r}^{\prime}(t)|}.\]
Since you're given $\mathbf{r}(t)$, it shouldn't be too difficult computing $\mathbf{r}^{\prime}(t)$ and it's norm $|\mathbf{r}^{\prime}(t)|$.

Can you take things from here?
 
Thanks for the help

The answer I worked out to be was
(10*t*i+6*t*j-5*k)/(sqrt(136*t^2+25))

I at first got it wrong because I tried this answer
(10*t+6*t-5)/(sqrt(136*t^2+25))

But that didn't account for the i,j,k in the original vector hence the answer is
(10*t*i+6*t*j-5*k)/(sqrt(136*t^2+25))

Thanks for the help guys and I hope this can help someone else
 
Last edited:

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