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Homework Help: Harmonic Motion of Oscillating Particle

  1. Mar 31, 2014 #1
    1. The problem statement, all variables and given/known data
    A particle moves along the x axis. It is moving initially at the position 0.280 m, moving with velocity 0.200 m/s and acceleration -0.450 m/s^2. Suppose it moves with constant acceleration for 4.10 s.

    (a) Find the position of the particle after this time.

    (b) Find its velocity at the end of this time interval.

    We take the same particle and give it the same initial conditions as before. Instead of having a constant acceleration, it oscillates in simple harmonic motion for 4.10 s around the equilibrium position x = 0.
    (c) Find the angular frequency of the oscillation. Hint: in SHM, a is proportional to x.

    (d) Find the amplitude of the oscillation. Hint: use conservation of energy.

    (e) Find its phase constant 0 if cosine is used for the equation of motion. Hint: when taking the inverse of a trig function, there are always two angles but your calculator will tell you only one and you must decide which of the two angles you need.

    (f) Find its position after it oscillates for 4.10 s.

    (g) Find its velocity at the end of this 4.10 s time interval.

    2. Relevant equations
    x(t) = A cos(wt + phi)
    w = sqrt(k/m)
    v = dx/dt = -w Asin(wt + phi)
    Vmax = w A = sqrt(k/m) A
    a = d^2x/dt^2 = -w^2 Acos(wt + phi)
    T = 2pi sqrt(m/k)
    f = 1/T
    w = 2pi f

    3. The attempt at a solution
    found a to be -2.68 m
    found b to be -1.65 m/s
    can't figure out c-g please help :(
  2. jcsd
  3. Mar 31, 2014 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    ... please show your working and your reasoning behind each of these answers, and you best attempt so far for the last ones: how you think about these problems will help me guide you.

    Guessing: for c. the acceleration is no longer constant.
    The given number is the instantaneous acceleration at the given position.
    (that help)

    Also you are missing an equation - very important one from the definition of SHM.
    Usually about the way the restoring force varies with position.
    Last edited: Mar 31, 2014
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