# Finding position at a time

• Dec 12th 2010, 04:49 PM
lancelot854
Finding position at a time
Find the particles position s at time t.

1.) $v=9.8t+5, s=10$ when $t=0$
2.) $a=32, v=20$ and $s=5$ when $t=0$

I think I got the first question, I ended up with $s(t)=4.9t^2+5t+10$, but I don't know what to do with the second problem. Any help is appreciated, thanks.
• Dec 12th 2010, 04:53 PM
snowtea
For the second question

s''(0) = a
so s'(t) = at + ?
s'(0) = v

Can you take it from here?
• Dec 12th 2010, 05:32 PM
lancelot854
Yeah, I get it now, thanks.
• Dec 13th 2010, 04:23 AM
HallsofIvy
Be careful about problem two. I would have interpreted "a= 32, v= 20, and s= 5 when t= 0" as meaning all three values are given at t= 0. In that case, you do NOT know the acceleration at any other time and cannnot answer the question. You have to assume that "a= 32" means that the acceleration is the constant 32 while v and s are given at t= 0.