Why is it important to have a control when making an experiment ? Also no web search or I will report so put it in own words answer ASAP please

Explain using examples, what is simple harmonic motion and why it is an important area of study in physics.

Explain the comparisons between nature and packingtown that appears on pages 81 and 82 answer

Awater balloon launcher uses an elastic band with a spring constant of 115 n/m to use thee launcher you stretch thee band back with a balloon n it the water balloons have a mass of 1.3 kg a) if you stretch the band by 0.8 m, what elastic force will the band exert? b) with the band stretched 0.8 m, how much elastic potential energy is stored in the spring? c) if you release the band, it pushes forward. what is the kinetic energy of the balloon when it reaches the natural length of the band? d) what is the speed of the balloon when it reaches the natural length of the band?