Physics Tutorial: Vibrational Motion

Introduction

• Vibrational motion involves wiggling, vibrating, shaking, and oscillating.
• Motion applies to a variety of objects, including atomic-level matter.
• Understanding vibrations and waves helps us understand light waves (sight) and sound waves (hearing).

Example: Bobblehead Dolls

• Bobblehead dolls illustrate vibrational motion.
• They have heads attached by a spring to a body and stand.
• Light taps cause the head to bobble, demonstrating back-and-forth movement which fades over time (damping).
• Questions to ponder:
  • Description of motion?
  • Change over time?
  • Differences between motions of different bobbleheads?
  • Quantities to measure motion?
  • Cause and cessation of motion?

Causes of Vibrational Motion

• Objects have a resting or equilibrium position with balanced forces.
• A force disturbing this equilibrium causes vibration (forced vibration).
• Forced vibration is momentary, causing diminishing motion.
• Damping is the loss of vibrational energy over time; energy dissipates to other objects.

Restoring Force

• Vibrating objects move past equilibrium due to inertia.
• Newton's first law of motion explains continued motion past equilibrium (balanced forces don't stop motion).
• Restoring force acts to return the object to equilibrium, differentiating vibrational from translational motion.

Other Vibrating Systems

• All objects can be forced to vibrate.
• Examples:
  • Pendulum: Mass on a string in equilibrium position, regular periodic motion.
  • Inverted Pendulum: Fixed end below vibrating mass (e.g., skyscrapers in wind, tuning forks).
  • Mass on a Spring: Mass vibrates about a fixed position, restoring force from spring.
• Damping observed in all systems, dissipating energy (e.g., air resistance in a pendulum).
• Damping is beneficial in systems like car suspension, preventing excessive motion.

Next Topics

• Properties of periodic motion.
• Quantitative description of vibrating objects and distinguishing measurements.