Topic

12.1 Simple Harmonic MotionDate, Section, Pages, etc.Mr. Richter

AgendaWarm UpAny paper stragglers?Intro to Simple Harmonic MotionNotes:Simple Harmonic MotionSprings and Hookes LawSimple PendulumsMotion and Energy in SHM

2Objectives: We Will Be Able ToIdentify 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 Hookes Law.

Warm UpA metronome keeps a ticking count of 90 beats per minute. What is its period of oscillation?What is its frequency of oscillation?Introduction to Simple Harmonic MotionWhat keeps an object bouncing up and down on a spring? What would cause this to stop?

Simple Harmonic Motion (SHM)Vibrations and WavesVibration: any repeated motion of an object moving back and forth, or oscillatingFansMass 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 displacementBasically: back-and-forth motion over the same path.Restoring Force: Object tends to want to return to original position. (Location is restored).Periodic meaning what?

8Hookes 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 Hookes Law

k = spring constant [N/m]Force (F) always in opposite direction of displacement (restoring!)

Many things behave like springs even if they are not actually springs.9The Simple PendulumMass is called bob. Assume string is weightless.Restoring force is a component of the weight of the bob.Fg = mgsinFor small angles, the pendulums motion is simple harmonic.

We will assume were only talking about small angle displacements10Energy During SHMTotal 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 Hookes Law.

Homeworkp. 441 #e,4p. 445 #1, 2, 4