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Explain the term 'wave velocity'. Write its SI unit.

A boat at anchor is rocked by wave whose crests are $100 \mathrm{m}$ apart and whose velocity is $25 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$. How often do the crests reach the boat?

Sound waves travel with a speed of about $330 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$. What is the wavelength of sound whose frequency is $550 \text{hertz}$?

A wave pulse on a string moves a distance of $8 \mathrm{m}$ in $0.05 \mathrm{s}$.

a. Find the velocity of the pulse.

b. What would be the wavelength of the wave on the same string if its frequency is $200 \mathrm{Hz}$?

Ocean waves of time period $10 \mathrm{s}$ have a speed of $15 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$. What is the wavelength of these waves?

A boat at anchor is rocked by waves whose crests are $100 \mathrm{m}$ apart. The wave velocity of the moving crest is $20 \raisebox{1ex}{$\text{m}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$. What is the frequency of rocking of the boat?

A longitudinal wave is produced on a toy slinky. The wave travels at a speed of $30 \raisebox{1ex}{$\text{cm}$}\!\left/ \!\raisebox{-1ex}{$\text{s}$}\right.$ and the frequency of the wave is $20 \mathrm{Hz}$. What is the maximum distance between the consecutive compressions of the slinky?  

A sound of wavelength $68 \mathrm{cm}$ travels $850 \mathrm{m}$ in $2.5 \mathrm{s}$. Calculate

a. the velocity of sound and

b. the frequency of sound.