Because the scientific method can go around in a circle as many times as neccisary to get the results you need
The length of the string must vary, while the angle and acceleration are constant
We have that The Density and Volume is given as

The factors that affect Density are Mass and Volume
From the question we are told that
The piece of wood shown above has a mass of 20 grams.
Wood parameters
2cm
5cm
3cm
Generally the equation for the Volume is mathematically given as

Generally the equation for the Density is mathematically given as

Therefore the factors that affect Density are Mass and Volume
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