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Mechanical Properties Of Fluids

Question
CBSEENPH11019974

Four identical hollow cylindrical columns of mild steel support a big structure of mass 50,000 kg. The inner and outer radii of each column are 30 cm and 60 cm respectively. Assuming the load distribution to be uniform, calculate the compressional strain of each column.

Solution
Given,
Mass of the big structure, = 50,000 kg
Inner radius of the column, r = 30 cm = 0.3 m
Outer radius of the column, R = 60 cm = 0.6 m
Young’s modulus of steel, Y = 2 × 1011 Pa
Total force exerted, F = Mg = 50000 × 9.8 N
Stress = Force exerted on a single column
        = 50000 × fraction numerator 9.8 over denominator 4 end fraction 
        =  122500 N 
Young's modulus, Y = fraction numerator Stress space space over denominator Strain end fraction
Strain space equals space fraction numerator open parentheses begin display style bevelled straight F over straight A end style close parentheses over denominator straight Y end fraction
where comma space

Area comma space straight A space equals space straight pi space left parenthesis straight R squared space – space straight r squared right parenthesis space equals space straight pi space left square bracket left parenthesis 0.6 right parenthesis to the power of 2 space end exponent – space left parenthesis 0.3 right parenthesis squared right square bracket space

Strain space equals space fraction numerator 122500 over denominator open curly brackets space straight pi space open square brackets left parenthesis 0.6 right parenthesis to the power of 2 space end exponent – space left parenthesis 0.3 right parenthesis squared space cross times space 2 cross times 10 to the power of 11 close square brackets close curly brackets end fraction space

space space space space space space space space space space space equals 7.22 space cross times space 10 to the power of negative 7 space end exponent

Hence comma space the space compressional space strain space of space each space
column space is space 7.22 space cross times space 10 to the power of negative 7 space end exponent.