Waves, frequencies and tones

I am a Swedish exchange student, it is the first time i am on this website and truthfully i am desperate.

I need to know how to solve these 4 basic questions.

1. The problem statement, all variables and given/known data

1. A feather is pulled out 4 cm if you hang 50 grams in it. If the spring is then loaded with a total of 150 grams and can pivot up and down the harmonic motion, which is the period?

2. A mass of 0.5 kg undergoing harmonic motion with a frequency of 2 Hz and an amplitude of 8mm. calculate:

a maximum speed of the Mass

b Maximum Acceleration of the mass

c The maximum force of the mass

3. A machine produces a certain distance of the sound level 87 decibels, how big would the noise level be if three such machines started simultaneously next to each other?

4. A string has a fundamental frequency of 294 Hz. then press down your finger on the string and it will be 25% shorter. What is the new frequency for the new basic tone that arise?

2. Relevant equations

3. The attempt at a solution

I tried to solve the 1st question and this is how far i came:

My solution: I started with Hooke’s law

f =-k * x

F =-k * x

-0.05 * 9.82 =-k * 0.04

0.491 = k * 0.04

0.491 / 0.04 =-k * 0.04 / 0.04

k = 0.491 / 0.04

k = -12.275


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