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instantaneous velocities

junglevan-disab
1-Newbie

instantaneous velocities

Given s=1+2t+t^2/4 [1,1+h] and find the velocity when t=1. I have worked the problem several times and continue to come up consistent answers, which are wrong by the way, I think I know how to come up with the avg. rate of change. I need to do this with out using the quotient rule. Thank you Dale
3 REPLIES 3

To find the velocity, you have to take the derivitive of the distance formula and then sub your points in.

On 11/7/2002 12:50:00 AM, junglevan wrote:
>Given s=1+2t+t^2/4 [1,1+h]
>and find the velocity when
>t=1. I have worked the problem
>several times and continue to
>come up consistent answers,
>which are wrong by the way, I
>think I know how to come up
>with the avg. rate of change.
>I need to do this with out
>using the quotient rule. Thank
>you Dale


Why do you need the quotient rule? Aren't you simply supposed to find the derivative --
ds/dt=2+t/2?

TTFN

Are you in the section of the book where you are to take the lim h->0 of (s(t+h)-s(t))/h ? This is a quotient equal to the average velocity but after expanding the numerator and dividing by h, you get terms with constants and powers of t, and other terms with products of powers of h. When h->0, the "h" terms go to zero, leaving what is later shown to be the derivative of s(t). THEN substitute t = 1 to find the slope at t=1.

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Physics: Common Sense made Obscure by Mathematics Don Sparlin
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