12.1 Simple Harmonic Motion
Date, Section, Pages, etc.
Mr. Richter
Agenda
 Warm Up
 Any paper stragglers?
 Intro to Simple Harmonic Motion
 Notes:
 Simple Harmonic Motion
 Springs and Hooke’s Law
 Simple Pendulums
 Motion and Energy in SHM
Objectives: We Will Be Able To…
 Identify the conditions of simple harmonic motion (SHM)
 Explain how force, velocity, and acceleration change as an
object vibrates with simple harmonic motion.
 Calculate the spring force using Hooke’s Law.
Warm Up
 A metronome keeps a ticking count of 90 beats per minute.
1. What is its period of oscillation?
2. What is its frequency of oscillation?
Introduction to Simple Harmonic Motion
 What keeps an object bouncing up and
down on a spring?
 What would cause this to stop?
Simple Harmonic Motion (SHM)
Vibrations and Waves
 Vibration: any repeated motion of an object moving back
and forth, or oscillating
 Fans
 Mass at the end of a spring.
 Pendulums.
 Waves are formed when a stationary substance vibrates.
 Ripples in water.
 Vibrating air with sound waves.
 Whipping a rope.
Simple Harmonic Motion (SHM)
 “any periodic motion that is the result of a restoring force
that is proportional to displacement”
 Basically: back-and-forth motion over the same path.
 Restoring Force: Object tends to want to return to original
position. (Location is “restored”).
Hooke’s Law (Springs!)
 Most mass-spring systems obey a simple (proportional) relationship
between force and displacement.
 This is also true of systems that can be modeled by a mass and spring.
 This relationship is called Hooke’s Law
 k = spring constant [N/m]
 Force (F) always in opposite direction of displacement (restoring!)
The Simple Pendulum
 Mass is called “bob”. Assume string is
weightless.
 Restoring force is a component of the weight of
the bob.
 Fg = mgsinθ
 For small angles, the pendulum’s motion is simple
harmonic.
Energy During SHM
 Total mechanical energy stays
the same.
 Trade off between potential
and kinetic energy.
Motion during Simple Harmonic Motion
Wrap-Up: Did we meet our objectives?
 Identify the conditions of simple harmonic motion (SHM)
 Explain how force, velocity, and acceleration change as an
object vibrates with simple harmonic motion.
 Calculate the spring force using Hooke’s Law.
Homework
 p. 441 #e,4
 p. 445 #1, 2, 4