Thank you.

It's been sometime since I've tackled highschool physics problems (doing Engineering in college atm), and I'm just working on these off the top of my head, so give me a good smack someone if I get them wrong.

 

1) For wave propagation, the energy associated with the wave front is directly proportional to the area covered by the wave front (energy conservation rules). In the case of a water wave, a 2 dimension wave that is, then Energy1/(2*pi*R1) = Energy2/(2*pi*R2)

 

In the case of 3 dimensional waves, then you use 4*pi*r^2 instead, as that is the formala for the surface area of a sphere instead of the circumference of a circle.

 

2) If the spring has a frequency of 2.81 rad/sec then in 1.42 seconds, it will be at the location of 3.9902 radians, or 228.63 degrees. Doing a sin(228.63), you get -0.7505 of unity. Since the max displacement is 0.232 meters, then this is when the spring is displaced at x1 = 0.232*0.7505 = 0.1741 meters. The associated potential energy is calculated using PE = 1/2(k)(x^2), probably in your equations list. Derivable from fundamentals using calculus. You can try, it's not too hard.

 

I hope those are right^^ Goodluck!