Yahoo Answers: Answers and Comments for Calculus  Physics Word Problem? [Physics]
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From Anonymous
enMY
Fri, 08 Dec 2017 02:51:54 +0000
3
Yahoo Answers: Answers and Comments for Calculus  Physics Word Problem? [Physics]
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From az_lender: dx/dt = t^2 + 2t  15.
This will be zero when ...
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Fri, 08 Dec 2017 03:39:43 +0000
dx/dt = t^2 + 2t  15.
This will be zero when t is 3 or 5 (but we're not considering negative times).
The particle is moving left at t = 0 but turns to the right at t = 3 and continues moving right thereafter.

From electron1: v(t) = t^2 + 2 * t – 15
t^2 + 2 * t – 15 = 0
...
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Fri, 08 Dec 2017 03:38:14 +0000
v(t) = t^2 + 2 * t – 15
t^2 + 2 * t – 15 = 0
t = [2 ± √(4 – 4 * 1 * 15)] ÷ 2
t = [2 ± 8] ÷ 2
t = 3 seconds and 5 seconds.
These are two times when velocity is 0 m/s. These are also the times the direction it is moving changes.

From Dr. Zorro: x(t)= (1/3)t^3 + t^2 15t + 2
v(t) = dx/dt
=...
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Fri, 08 Dec 2017 03:25:58 +0000
x(t)= (1/3)t^3 + t^2 15t + 2
v(t) = dx/dt
= t^2 + 2t 15
= (t+5)(t3)
v(t)=0 => t=3
v<0 when 0<t<3
v>0 when 3<t<8
The particle turns at t=3. It turns to the right.