Travelling Waves

Physics 101

Wave-a motion of disturbance Waveform-shape or pattern of wave Pulse-disturbance of short duration . Shape of

pulse depends on the motion of the source that generates the pulse.

Continuous wave-continuous wave that re-peats over and over again.

Wave cycle-continuous wave that repeats over and over again.

Terminologies

Mechanical wave-travels through physical ma-

terial or medium (ex. vibration of violin string, water ripples, seismic waves in Earth’s crust)

Terminologies

https://sites.google.com/a/xcp.org/xcp-physics/ap-physics/oscilla-tory-motion/mechanical-waves

Electromagnetic waves-waves generated by

charged particles that accelerate and do not need medium to travel.

Terminologies

http://chemwiki.ucdavis.edu/Physical_Chemistry/Spectroscopy/Fundamentals/Electromagnetic_Radiation

1. Transverse Waves

2. Longitudinal Waves

Two Types of Travelling Waves

A wave in which the displacement is perpendicular to

the direction in which the wave travels. Ex.) A wave on a rope is a transverse wave. Light and

other electromagnetic waves are also transverse waves.

Ex.) S wave or secondary wave is the second wave you feel in an earthquake which displace the ground up and down.

https://www.youtube.com/watch?v=UHcse1jJAto

Transverse Wave

http://www.phy-astr.gsu.edu/dhamala/Physics2211/Chapter20.pdf

Particles in the medium move parallel to the

direction which the wave travels. Ex.) P wave or primary wave during an earth-

quake. P waves are also known as compres-sional waves, because of the pushing and pulling they do.

https://www.youtube.com/watch?v=aguCWnbRETU

Longitudinal Wave

http://www.phy-astr.gsu.edu/dhamala/Physics2211/Chapter20.pdf

The speed of transverse waves on a string

stretched with tension T is

Wave Speed

http://www.phy-astr.gsu.edu/dhamala/Physics2211/Chapter20.pdf

You decide to train your dog, Ruby, to run

faster. You hang a 1.5m long string with a mass of 2.0g to a wall and horizontally stretch by 0.50m away. The string is tied to your dog’s treat. You know that the wave pulse travels along the stretched string at 20m/s. Your dog cannot catch the treat if the mass is smaller than 0.055kg. Will your dog be able to catch the treat?

Example Question

The treat is in static equilibrium, hence

Tension in the string is The linear density is 0.002kg/1.5m=0.001333kg/m

Then,

Therefore, your dog cannot catch the treat!

Solution

(0.0013333kg/m)

(20m/s) 0.054kg