I need someone to go over my answers please, I was haveing trouble on these three. If I got it wrong will you tell me how I should solve it with formulas please.

Question

What is the wave speed for a wave of 5 meters wavelength that has a frequency A) 25.6 m/s.
B) 64 m/s.
C) 128 m/s.
D) 640 m/s.
I think its a

A string on a guitar is 0.4 m long and produces 360 Hz as its fundamental tone. If you press on the string so that you reduce its free length to 0.2 m, what tone will it produce?

A) 270 Hz.
B) 480 Hz.
C) 540 Hz.
D) 720 Hz.
I think it is D

You have a tuning fork that produces a frequency of 512 Hz in air. You submerge it in the swimming pool and strike it against the wall underwater. The speed of sound in water is 1500 m/s. What will the resulting frequency and wavelength be?

A) 740 Hz, 3.41 m
B) 740 Hz, 0.773 m
C) 512 Hz, 3.41 m
D) 512 Hz, 2.93 m

Answer 1

In the first question, you did not provide the frequency.

Your answer to the second question is correct.

In the third question, the frequency remains the same under water and (1500 m/s)/(frequency) is the new wavelength.

Answer 2

i think the first question the answer is A. wavespeed=frequency x wavelength
freq=128hz
wavelength=5 meters
so multiplied equals 640