The velocity of the wave on the string is given by

Solving the above equation,

The frequency of the wave
and wave length is 
The velocity is 
Substituting numerical values,

The length of the string is 
Answer:
D. The primary source, because it was written by the researcher
Explanation:
One should learn to trust the primary source more because it is the real work of the researcher.
A primary work defines the work of research from his or her experimental findings.
- The primary source presents experimental data and other subordinates ones to reach a conclusion as seen from the view of the researcher.
- A secondary source implies someone else documenting their own opinion about the primary experimental set up.
- This can get dicey in the sense that results can be twisted to serve other ulterior motives.
Answer: Sorry the pic is too blurry try making the resolution higher
Yes, a puddle of water is an object in motion.