ASRJC Oscillations Notes

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 10-1 Additional Notes Topic 10: Oscillations Content: • Simple harmonic motion • Energy in simple harmonic motion • Damped and forced oscillations, resonance Learning Outcomes: Candidates should be able to: (a) describe simple examples of free oscillations. (b) investigate the motion of an oscillator using experimental and graphical methods. (c) show an understanding of and use the terms amplitude, period, frequency, angular frequency and phase difference and express the period in terms of both frequency and angular frequency. (d) recall and use the equation a = -ω2x as the defining equation of simple harmonic motion. (e) recognise and use x = xo sin ωt as a solution to the equation a = -ω2x. (f) recognise and use v = vo cos ωt and v = ±ω ( ) 22 oxx − (g) describe, with graphical illustrations, the changes in displacement, velocity and acceleration during simple harmonic motion. (h) describe the interchange between kinetic energy and potential energy during simple harmonic motion. (i) describe practical examples of damped oscillations with particular reference to the effects of the degree of damping and the importance of critical damping in cases such as a car suspension system. (j) describe practical examples of forced oscillations and resonance. (k) describe graphically how the amplitude of a forced oscillation changes with driving frequency near to the natural frequency of the system, and understand qualitatively the factors which determine the frequency response and sharpness of the resonance. (l) show an appreciation that there are some circumstances in which resonance is useful and other circumstances in which resonance should be avoided.

ANDERSON SERANGOON JUNIOR COLLEGE PHYSICS 9749 10-2 Additional Notes A.1 Periodic Motion • Any motion that repeats itself in equal time intervals. Examples: (a) mass oscillating at end of a spring (b) oscillation of a simple pendulum (c) planetary motion A.2 Oscillatory or Vibratory Motion • A particle in oscillatory or vibratory motion moves back and forth over the same path. Examples: (a) mass oscillating at end of a spring (b) oscillation of a simple pendulum (c) vibrations of strings in musical instrument Oscillation Free Oscillation Forced oscillation (dealt with later in Section E) the to-and-fro movement of a body about a fixed point in which no external driving force acts on it. Occurs when the body is acted upon by an external periodic driving force, causing the body to oscillate at the frequency of the periodic force , rather than the natural frequency of the body. Example: A child on a swing given a n initial push and swings freely. Example: A child on a swing kept in motion by pushing the child at equal intervals of time. Nature of Science We can gain a deep understanding of periodic motion by analys