Question

The position function of a particle is given by r(t)=⟨−1t2,−4t,t2+4t⟩.
At what time is the speed minimum?

Answer 1

I got about as far as finding the magnitude of the velocity vector which is sqrt(8t^2+16t+32) but not sure where to go from here.

Answer 2

set d/dt (speed) = 0. in other words, a(t) = 0

Answer 3

yeah, so it should be sqrt(32). i tried that and it didn't work.

Answer 4

oh, wait, i have to integrate the whole sqrt thing again and set that equal to 0? grr....

Answer 5

not integrate. Differentiate. and yeah you do that again

Answer 6

ok thanks. lemme see if that works

Answer 7

it worked. thanks @sourwing !

Answer 8

no prob