Standing Waves help 30 mins left.

[evgeniy]

Standing Waves help! 30 mins left.

Hello everyone who's here, so far I've been doing great on waves, but what the heck is standing eave?

Here is a problem that I kinda get, but not completely:

Two strings, with the same mass/length m oscillate with the same frequency f=2.00 Hz. The first string has length L1, tension T1 and vibrates in the fundamental mode (n=1). The second string has length L2, tension T2 and vibrates in the third harmonic (n=3). Assuming L2=2.30 L1:

a) What is the ratio T1/T2?

b) What would be the frequency of the second string if it oscillates in the mode n=1?

what the hell is fundamental mode?
please help, or at least give hints,
thanks a lot

 

[evgeniy]

well it's kinda late now, and i got the answers here:

1) 1.70
2) 0.667 Hz

Can anyone tell me how to get them at least so i know how to do them on the test?? (formulas may be)?

 

[Dr.Brain]

Main fomulae:

L= (2n-1)(wavelength)/4

and velocity=(frequency)(wavelength)

where L=length of string

 

[evgeniy]

are u saying to find wavelength first?
what about the tension?

 

[OlderDan]

are u saying to find wavelength first?
what about the tension?

The speeds of the waves are equal to sqrt(tension/mass per unit length). Since the masses are the same, ratio of speeds will be the square root of the ratio of tensions.