Tutorial Week 10

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Worksheet Questions

  1. A undamped mass-spring system with mass 1 kg and spring constant 16 kg/s$^2$, is initially at rest. At $t=3$, a linearly increasing force is applied until the force reaches $F_0 = 10$ N at $t=8$. After that moment, the force remains constant at that level ($F_0$).
    1. Write down the forcing function for this scenario in terms of Heaviside functions.
    2. Write down the ODE for this mass-spring system subject to the given forcing function.
    3. What is the transfer function ($H(s)$) and the impulse response ($h(t)$) for this ODE?
    4. Use the impulse response and convolution to solve the ODE from part (b).
  2. Consider the following differential equation:$$ y''+\omega^2 y=\frac{2}{\pi}\cos(t)$$ where $\omega=2.01$.
    1. Find a particular solution $y_p(t)$ using the method of undetermined coefficients.
    2. Now consider the equation $$ y''+\omega^2 y=\sum_{n=1}^{10}\frac{2}{n\pi}\cos(nt).$$ Use your solution in (a), and again the method of undetermined coefficients, to determine a particular solution $y_p(t)$.
    3. Describe how the magnitude of the coefficients in your particular solution varies with n.

Tutorial Week 10 Solutions