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A particle moves with acceleration `a(t)`  m/s^2 along an s-axis and has velocity...

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user7230927 | (Level 1) Salutatorian

Posted August 12, 2013 at 5:34 PM via web

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A particle moves with acceleration `a(t)`  m/s^2 along an s-axis and has velocity `v_0`  m/s at time `t=0`  .  Find the displacement AND the distance traveled by the particle during the given time interval.

`a(t)=9 ; `

`v_0=-1 ; `

`0lt=tlt=2`

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted August 12, 2013 at 5:40 PM (Answer #1)

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The particle moves along a straight line with initial velocity `v_0` = -1 m/s and acceleration a(t) = 9 m/s^2. The distance traveled by the particle during a duration of time equal to t is `s = v_0*t + (1/2)*a(t)*t^2` .

Substituting the given values the displacement of the particle in the period from t = 0 to t = 2 is:

(2 - 0)*9 + (1/2)*9*(2 - 0)

=> 18 + 9

=> 27

The particle travels 27 m in the given interval.

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user7230927 | (Level 1) Salutatorian

Posted August 12, 2013 at 5:50 PM (Reply #1)

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Thank you for your response. Wiley Plus is saying 27m is incorrect. I should have mentioned it, but we are asked to solve using integration, where: 

displacement= `int_(t_0)^(t_1)v(t)dt`

and distance traveled = `int_(t_0)^(t_1)|v(t)|dt`

I found that displacement = 16, but am not sure where I went wrong trying to obtain distance traveled (it does not equal 16, atleast according to wiley)  Thank you in advance if you are able to help clarify.

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted August 12, 2013 at 7:10 PM (Answer #2)

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`a(t) = (dV(t))/(dt)`

`dV(t) = a(t)dt`

`intdV(t) = inta(t)dt`

`V(t) = int9dt`

`V(t) = 9t+C`

`V(0) = 9xx0+C`

`-1 = C`

`V(t) = 9t-1`

`V(t) = (dS(t))/(dt)`

`S(t) = intV(t)dt`

`S(t) = int(9t-1)dt`

`S(t) = 9t^2/2-t+D` where D is a constant.

It is given that the time interval is `0<=t<=2`

Displacement of particle `= S(2)-S(0)`

Displacement of particle `= (9xx4/2-2) = 16m`

For distance travelled;

`S(t) = int_0^2(9t-1)dt`

`S(t) = [9t^2/2-t]_0^2`

`S(t) = (9xx4/2-2) = 16`

So the displacement and distance travelled by the particle is 16m.

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