Homework Help: Physics

Posted by James on Thursday, July 12, 2012 at 4:19pm.

A 48-cm-long wire with a mass of 11.0 g is under a tension of 50.5 N. Both ends of the wire are held rigidly while it is plucked.

(a) What is the speed of the waves on the wire?
(b) What is the fundamental frequency of the standing wave?

The answers are 50.5 m/s and 48.9 Hz respectively. How do I get these answers?

Physics - James, Thursday, July 12, 2012 at 4:21pm
For part (a) I've been doing the following work:

u=M/L; where u= mass per unit length
u=(0.011)/(.48)= 0.022916667

v= sqrt(T/u); where T = tension
v= sqrt(50.5/0.022916667) = 47.0 m/s
Physics - James, Thursday, July 12, 2012 at 4:22pm
I'm not really sure how to figure out part (b); however, I'm sure that it's answer relies on me figure out part (a) correctly.
Physics - Elena, Thursday, July 12, 2012 at 4:45pm
Your answer for part A is correct.
Velocity in the stretched string is
v = sqrt(T/m(o)).
=sqrt(50.5•0.48/0.011)=46.94 m/s

Part B

Part B
λ =2 L= 0.96 m.
λ =v/f,
f=v/ λ =46.94/0.96=48.9 m
Physics - James, Thursday, July 12, 2012 at 4:54pm
Thank you. I guess WebAssign made a mistake.
Physics - James, Thursday, July 12, 2012 at 5:03pm
Also, shouldn't f=48.9 m be f=48.9 Hz?
Physics - Elena, Thursday, July 12, 2012 at 5:19pm
Certainly, Hz

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