A string along which waves can travel is 2.50 m long and has a mass of 203 g. The tension in the string is 26.0 N. What must be the frequency of traveling waves of amplitude 7.70 mm in order that the average power be 85.0 W?

Answer 1

complicated. Power will have to do with amplitude and time.

find wavespeed.
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/string.html#c2

Then, energy and power can be calculated.
http://hyperphysics.phy-astr.gsu.edu/hbase/waves/powstr.html

Answer 2

I'm having some trouble using these sites