Acceleration from Velocity How would you find the acceleration of an automobile at $t$ seconds from the formula giving velocity $v(t)$ in $ft/sec$:
$$v(t) = \frac{85t}{6t+16}$$
$5$ seconds ? _____$ft/sec^2$
$10$ seconds ? _____$ft/sec^2$
$20$ seconds ? _____$ft/sec^2$
Do I use the formula:
$$a = \frac{v_1 - v_0}{t_1-t_0}$$
or
$$a = \frac{340}{(3t+8)^2}$$
Thanks,
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Update 1—According to comments, I should use the first derivative of the velocity equation. The answers I calculated are $.643, .235$, and $.074$. Would I need to divide by seconds?
Update 2—Thanks for all your help. The aforementioned values were correct! :D

Just differentiate your velocity vector V(t) to get A(t) .Plug in 5,10,15 to get answer
