Frequency is no. of times this wave vibrates or complete its one cycle per unit time. As it vibrates 30000 times per second its frequency is 30000 per second or 30000 Hz [1 Hz = once per second].
The answer is P-waves and S-waves
Velocity = distance / time
v = (15*1000)m / (2*60*60)s
v=2.08 m / s
I would say friction because it requires to surfaces in order for the force to take place
correct me if I'm wrong.
