Physics
Oscillations and resonance
- 1.
An oscillator executes simple harmonic motion (SHM) with angular frequency 5.0 rad s^-1. Calculate acceleration at displacement +0.080 m from equilibrium and explain the sign.
[3 marks] - 2.
A mass 0.250 kg oscillates on a spring of stiffness 40.0 N m^-1. Find the period. Assume a massless spring and negligible damping.
[3 marks] - 3.
A 0.200 kg oscillator executes simple harmonic motion (SHM) with amplitude 0.0500 m and omega = 10.0 rad s^-1. Find its speed and kinetic energy when its displacement from equilibrium is x = 0.0300 m. Neglect damping.
[3 marks] - 4.
An SHM displacement is x = 0.0400cos(4.00t) m, with t in seconds. Find the first positive time at which x = 0.0200 m and the signed velocity then, to 3 significant figures.
[3 marks] - 5.
A pendulum has length 0.800 m and small amplitude. After moving to a location with unknown g its measured time for 20 complete periods is 36.0 s. Estimate g and its percentage uncertainty if total timing uncertainty is +/-0.2 s and length uncertainty +/-0.005 m. Use a worst-case first-order uncertainty sum.
[4 marks] - 6.
For weak damping the amplitude envelope is A(t) = A0 e^(-0.120t), with t in seconds and constant oscillator stiffness. Using a slowly varying envelope model in which cycle-averaged mechanical energy is approximately proportional to A^2, find the approximate time for that energy to fall to one quarter of its initial value. Explain why maximum forced-response amplitude need not occur exactly at the undamped natural frequency.
[3 marks]
Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.