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The displacement (in centimeters) of a particle moving back and forth along a straight line is given by the equation of motion

s = 2 sin(πt) + 2 cos(πt),
where t is measured in seconds. (Round your answers to two decimal places.)
(a) Find the average velocity during each time period.
(i) [1, 2]
cm/s

(ii) [1, 1.1]
cm/s

(iii) [1, 1.01]
cm/s

(iv) [1, 1.001]
cm/s

(b) Estimate the instantaneous velocity of the particle when t = 1.
cm/s

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4 answers
  1. https://www.jiskha.com/questions/1813507/the-displacement-in-centimeters-of-a-particle-moving-back-and-forth-along-a-straight

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    Damon
  2. I will do iii) you do the rest in the same way
    s = 2 sin(πt) + 2 cos(πt)
    [1, 1.01] cm/s
    when t = 1
    s = 2sinπ + 2cosπ = 0 - 2 = -2
    when t = 1.01
    s = 2sin(1.01π) + 2cos(1.01π) = -2.0618346...

    avg velocity = change in distance/change in time
    = (-2.0618346.. - (-2))/(1.01-1) = -6.183 or -6.18 correct to 2 decimals

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    Reiny
  3. careful, displacement not distance (vector)
    lol, I did part iii too

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    Damon
  4. By the way they luckily asked for displacement and velocity, not average distance and speed. If they asked for the scalars and not the vectors you would have to be careful about going back and forth. If you go all the way around a circular track your displacement and average velocity is ZERO. However your distance is pi D and speed is pi D/time

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    Damon
    today at 5:41pm

    This problem is trying to get you to converge to the speed at t = 1
    which we know is -2 pi
    so try the part iii for example
    s(1.01 ) = 2 sin(1.01 pi ) + 2 cos(1.01 pi)
    = -0.0628 -1.999 = -2.062
    s(1) = 2(0)+2(-1) = -2
    so
    s(1.01)-s(1) = -.062
    divide by time of 0.01 seconds
    v average = -6.1813
    the exact from the second part was -2 pi = - -6.2318 .......
    if you did 1 to 1.0001 seconds it would be even closer

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    Damon

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