Answer:
The dependent variable is the variable that is studied while the independent variable is the variable that is being manipulated
As we know that Nth harmonic of the string is given by

now here we will have




now from above formula we have


now for first harmonic N = 1

for second harmonic N = 2

for third harmonic N = 3
Answer:
1) you could put more force behind it. (increase) 2) have another object interact with that object. (increase or decrease) 3) the object could hit a wall and stop or slow down (decrease)
Sorry if wrong