1. Barry Latham Physics: Principles & Problems Glencoe Science, 2005

2. 14.1: Periodic Motion Periodic motion- repeating motion in a regular cycle Simple harmonic motion- the restoring force is proportional to the displacement from the equilibrium position Period (T, s)- time needed to complete one full cycle Amplitude- maximum displacement from the equilibrium position Physics Physlets I.16.1

3. The Mass on a Spring The force on a hanging spring at rest is equal to mg More mass  more Force  more displacement Hooke’s Law F sp =-kx The force exerted on a spring is equal to the spring constant (k) times the distance (x in m) the spring is moved from equilibrium k represents the stiffness of the spring (N/m) The negative sign refers to the Force being restorative

4. Potential Energy in a Spring When a spring is stretched or compressed, it is storing energy! PE sp =(½)kx 2 When we graph PE vs x, we see that the slope equals N/m (spring constant!) Area of the graph equals Nm (Joules!) When F g =F sp, then the spring has achieved equilibrium Physics Physlets I.16.3, E.16.2

5. Pendulums Pendulum- a massive object (bob) suspended by a string or rod of length, L F net = mgsin  F T =force of tension along the string or rod (mgcos  ) F g =force of gravity, always pointing down

6. Period of Pendulum T=2  √ (L/g) T=period (s) L=length of pendulum support (m) g=acceleration due to gravity (m/s 2 ) No mention of what the bob’s mass is!

7. Resonance Resonance- when small forces are applied at regular intervals to increase the amplitude of vibration Pushing someone on a swing to make them go higher Jumping several times on a diving board before diving Tacoma Narrows Collapse http://www.youtube.com/watch?v=HxTZ446tbzE Physics Physlets E16.7

8. 14.2 Wave Properties Mechanical Waves Wave- a disturbance that carries matter or energy through space Periodic wave- has a regular period Wave pulse- a single bump or disturbance

9. Transverse Wave Transverse waves- motion of the medium moves perpendicularly to the direction the energy travels Ropes, surface water waves, stringed instruments Electromagnetic waves Physics Physlets I.17.1 (Animation 1 & 2)

10. Longitudinal Waves Longitudinal waves- motion of the medium moves parallel to the direction the energy travels Slinky pulled back Physics Physets I.17.1 (Animation 3)

11. Measuring a Wave Wavelength (, m)- distance from one point on a wave to the same point repeating Crest- high point on a wave Trough- high point on a wave Frequency (f, Hertz=1/s)- the number of peaks that pass per second Period (T, s)- the amount of time that passes from one peak to occur until the next peak occurs T=1/f

12. Wave Speed Speed (m/s)- v= /T Phase (  )- the displacement of one wave’s peak from another’s peak 100% In phase- peaks match up 100% out of phase- peak matches up to trough Amplitude- height from equilibrium to peak

13. 14.3 Wave Behavior Waves at Boundaries Boundary- a change in medium Air to water, stiff spring to soft spring, etc. Incident wave- wave that strikes the boundary Reflected wave- the returning wave All of the wave is not reflected, some passes through to second medium

14. Interference Principle of Superposition of waves Book definition: The displacement of a medium caused by two or more waves is the algebraic sum of the displacement caused by the individual waves Easy Definition: Add the waves’ amplitudes to get a new wave Physics Physlet I.17.3

15. Wave Interference Node- the point at which a wave doesn’t move at all Mid-point of trough and crest Antinode- the point at which the wave moves the most Highest part of crest or trough Standing wave- a wave that perfectly fits the length of the object Always in odd multiples of ½ ( =one full wavelength) See page 389 a=(1)(½ ), b=(3)(½ ), c=(5)(½ )

16. Waves in 2D Wave front- a line that represents the crest of a wave Can be circular or straight Ray- represents the direction of travel and is perpendicular to the wave front Angles are measured from the Normal to the reflection surface Law of Reflection- the angle of incidence equals the angle of reflection

17. Refraction Law of Refraction- when changing mediums, a wave is bent (changes direction) instead of reflected Physics Physlets I.34.1