Answer:
f1 = 12.90 Hz
Explanation:
To calculate the first harmonic frequency you use the following formula for n = 1:

( 1 )
It is necessary that the unist are in meters, then you have:
L: length of the string = 60cm = 0.6m
M: mass of the string = 0.05kg
T: tension on the string = 20 N
you replace the values of L, M and T in the expression (1) for getting f1:

Hence, the first harmonic has a frequency of 12.90 Hz
Answer: Gravitational potential energy changes.
Explanation: This is because depending on the amount of mass in an object that’s the amount of gravity pulling you down to the center of the earth
Av Speed = total distance / time time = 32+ 46 / 2.7 = 28 m/sec
Av velocity = total displacement / time total = S / t
S = sqrt( 32^2 +46^2) = 56 m
Av Velocity = 56/ 2,7 = 20.75 m/sec
with angle tan^-1 = 0.7 north west ( about 35 degrees north west)