The equation of motion of a particle is
s = t^3 − 3t,
where s is in meters and t is in seconds. (Assume t ≥ 0.)
(a) Find the velocity and acceleration as functions of t.
I got v(t) =3t^2 -3 which is correct
I got a(t) = 6t which is correct
(b) Find the acceleration after 7 s.
I got 42 which is correct

BUT im stuck here!!!!!!
(c) Find the acceleration when the velocity is 0.
i guess -3 and 0 but both wrong i cant figure it out! please help!

Question

The equation of motion of a particle is 
s = t^3 − 3t,
 where s is in meters and t is in seconds. (Assume t ≥ 0.)
(a) Find the velocity and acceleration as functions of t.
I got v(t) =3t^2 -3 which is correct
I got a(t) = 6t which is correct
(b) Find the acceleration after 7 s.
I got 42 which is correct

BUT im stuck here!!!!!!
(c) Find the acceleration when the velocity is 0.
i guess -3 and 0 but both wrong i cant figure it out! please help!

abmon98 · Answer

i think its going to be 6ms^-2

anonymous · Answer

it cant be, because for my question the answer is left blank then has ms^2 after it.

anonymous · Answer

i think i read somewhere where you take a double derivative, but I had trouble understanding it. i could be wrong though.

abmon98 · Answer

0=3t^2-3
3t^2=3
t^2=1
t=+or-1 
it cannot be -1
so we substitute the 1 into the 6t giving us an answer of 6

anonymous · Answer

AHHHH that makes sense!!! thank you!