(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A car's velocity can be described by v=6-0.3s. Find its acceleration at t=100s

2. Relevant equations

v=ds/dt, a=dv/dt

3. The attempt at a solution

This was actually a two part question, where the first part required you to find s at t=100.

So I wrote:

ds/dt = 6-0.3s and integrated that equation to get:

s=(e^{-0.3t}-6)/(-0.3)

From which I found that at t=100s, s=20m

For the second part,

a=dv/dt=(dv/ds)*v

To find dv/ds term, I took the derivative of v=6-0.3s and got v'=-0.3. I put the known formulas into the equation above to get:

a=-0.3(6-0.3s)

I know that at t=100s s=20, so I can find the acceleration at t=100 (equivalent to s=20):

a=-0.3(6-0.3*20)=0

I think my thought process makes sense (it usually does), but I might be doing something stupid and not realizing it. Long story short, I just don't like a=0. However, I know some people got 0 as well and some actually got a number (this was on a midterm).

Is it right? And if not, can you please point out the area where I'm doing something wrong?

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# Homework Help: Dynamics question

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