kinematic problem

[Dell]

a body moves according to the following:
ay=2-4t
ax=-1
vy=2t-2t2
vx=1-t
x0=2
y0=3

what is the tangential acceleration when t=1?
what is the radius of curvature of the motion when t=1?

aT=\vec{a}dot\vec{v}/|v|
at t=1, \vec{v}=0 so there is no tangential acceleration, how can this be true???

the secon part of the question is also not making sence

ar=v2/r, but here v=0 and ar=3 since there is no aT and ax=-1, ay=-2????

[LowlyPion]

I think what the question is asking is what is the linear acceleration at t=1 given by the expression of the acceleration vector at that time. Isn't this merely a matter of evaluating the a(t) function at t=1?

For the radius of curvature, I would suggest:
http://www.intmath.com/Applications-differentiation/8_Radius_curvature.php