I'm not from that school but I can help you.
D. Equal to zero.
Because the forces balance each other.
Answer:
Using g = 9.8: 1.02 kg, Using g = 10: 1 kg
Explanation:
E = mgh
20 = m(9.8)(3 - 1)
20 = 9.8m(2)
20 = 19.6m
m = 1.02 kg
I'm now assuming you may be using a g constant of 10, thus the close integer result, in which case the mass would be exactly 1 kilogram.
Weight = mg, g ≈ 9.8 m/s²
Weight = 2.2 * 9.8 ≈ 21.56 N
Fperson =[( velocity of wind )+ or - (velocity of person)] / [(velocity of wind) + or - (velocity of sounds)] x frekuency of sounds
