Go Back   Physics Help Forum > College/University Physics Help > General Physics

General Physics General Physics Help Forum

LinkBack Thread Tools Display Modes
Old Jan 25th 2018, 06:43 PM   #1
Junior Member
Join Date: Jan 2018
Posts: 1
The adding of 3 waves.

I have been stuck on this problem for hours and i cant seem to find any information or anything online that makes since to me.

There are 3 waves traveling in the +x direction, what is the amplitude, phase and speed of the resulting wave?

Not to seem ignorant, but i am not sure what it is i am even suppose to do. My initial though was to add the first two together, so my amplitude would be 7, but i am not sure what to do with the phase shift. I thought maybe 7cos1 as new amplitude but nothing online seems to give me any information, everything is in sin and we are being "taught' everything in cos, so i assume things just switch a bit? would the new phase be (1-pi/2) and would the rsulting speed be (2pi/14)(2600/2pi)? much help is appreciated.
Jacoza is offline   Reply With Quote
Old Jan 26th 2018, 04:29 AM   #2
Senior Member
Join Date: Oct 2017
Location: Glasgow
Posts: 395
There is an identity:

$\displaystyle a \cos x + b \sin x = R \cos (x- \alpha)$


$\displaystyle R = \sqrt{a^2 + b^2}$
$\displaystyle \alpha = arctan\left(\frac{b}{a}\right)$

I think that this identity together with

$\displaystyle \cos x = \sin \left(\frac{\pi}{2} - x\right)$

should be enough to solve your problem. Basically, you will want to use the above formula to decompose your cosine waves into a mixture of sine and cosine waves where the phase difference is separated out into the sine part. Then you can add up the separate contributions.
benit13 is offline   Reply With Quote

  Physics Help Forum > College/University Physics Help > General Physics

adding, waves

Thread Tools
Display Modes

Similar Physics Forum Discussions
Thread Thread Starter Forum Replies Last Post
Adding Vectors mirandaeb Kinematics and Dynamics 1 Oct 8th 2013 11:30 AM
Adding Vectors I J K Method HELP angelohastie Advanced Mechanics 3 Sep 17th 2013 03:40 PM
Adding vectors by components Sml2382 General Physics 4 Nov 14th 2012 10:17 AM
Need help with adding vectors! tonic22 Kinematics and Dynamics 1 Feb 20th 2011 03:50 PM

Facebook Twitter Google+ RSS Feed