# Math Help - Instantaneous Velocity calculus

1. ## Instantaneous Velocity calculus

s(t)= -16t^2 + 400t + 5

What is the Instantaneous Velocity after 8 sec?

I'm not exactly sure what to do..

2. ## Velocity

Hello civiliam
Originally Posted by civiliam
s(t)= -16t^2 + 400t + 5

What is the Instantaneous Velocity after 8 sec?

I'm not exactly sure what to do..
The velocity at any instant is given by the value of $\frac{ds}{dt}$ at that instant. So you need to differentiate your function (are you OK with that?), to get a formula for $\frac{ds}{dt}$ in terms of $t$. Then plug in the value $t = 8$. (You should get the answer $144$.)

Can you complete it now?